<PAGE>   1

                                                                   Exhibit 10.42


                            ASSET PURCHASE AGREEMENT




                                      Among





                             James and Norma Fosgate

                                       and

                              Rockford Corporation







                           Dated: September 21, 2000



Confidential Treatment Requested. Confidential portions of this document have
been redacted and have been separately filed with the Commission.
<PAGE>   2
                            ASSET PURCHASE AGREEMENT

                  This Asset Purchase Agreement is among James and Norma Fosgate
("Fosgate") and Rockford Corporation ("Rockford"). In consideration of the
mutual covenants and agreements in this Agreement, Fosgate and Rockford agree as
follows:

1.       BACKGROUND AND DEFINITIONS.

         1.1      Rockford Business. Rockford manufactures and sells car, home,
                  and professional audio products.

         1.2      Asset Sale. Fosgate desires to sell, and Rockford desires to
                  purchase (a) the names "Fosgate-Audionics" and "Audionics" and
                  any federal or state registrations relating to these names
                  (the "Names") and (b) all of the goodwill associated in any
                  way with the Names (the "Goodwill"and, together with the Names
                  the "Assets").

         1.3      Purpose. The purpose of this Agreement is to state the terms
                  of Fosgate's agreement to sell, and Rockford's agreement to
                  purchase, the Assets.

         1.4      Definitions. In this Agreement:

                  Agreement means this Asset Purchase Agreement and each of the
                  Schedules and certificates delivered with this Agreement. The
                  Schedules and certificates are a part of this Agreement;

                  Assets means the Assets described in Section 1.2;

                  Business means the manufacture and sale of car, professional,
                  and home audio equipment, products, and accessories;

                  Closing means the consummation of the transactions
                  contemplated by this Agreement.

                  Closing Date means the day on which the Closing actually takes
                  place;

                  Contract means any contract, indenture, mortgage or deed of
                  trust, lease, guaranty, insurance policy, bond, license,
                  instrument, understanding, obligation, or other agreement;

                  Encumbrance means any mortgage, pledge, lien, claim, charge,
                  security interest, restriction, or other encumbrance;

                  Government means any legislature, executive, department,
                  administrative agency, municipality, subdivision,
                  instrumentality, or other authority of the United States, any
                  state, or any foreign country;
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                  Information means information supplied to Rockford by Fosgate
                  under this Agreement;

                  Law means any law, statute, ordinance, rule, regulation,
                  order, judgment, injunction, or decree;

                  Fosgate means James and Norma Fosgate;

                  Order means any order, decree, decision, injunction, finding,
                  or judgment;

                  Permits means all approvals, permits, licenses, filings,
                  registrations, certificates, orders, authorizations,
                  qualifications, or other consents from any Government,
                  self-regulatory authority, or any other third party;

                  Proceeding means any claim, action, suit, mediation,
                  arbitration, labor grievance, Government investigation, or
                  other legal or administrative proceeding;

                  Purchase Price means the purchase price of the Assets
                  established in Section 4; and

                  Rockford means Rockford Corporation, an Arizona corporation;

2.       PURCHASE AND SALE OF ASSETS; NO ASSUMPTION OF LIABILITIES.

         2.1      Purchase of Assets. At the Closing, Fosgate will convey to
                  Rockford, and Rockford will purchase, all of Fosgate's right
                  and interest in the Names and Goodwill free and clear of any
                  Encumbrance through Fosgate. Rockford acknowledges that
                  Fosgate makes no representation or warranty with respect to
                  Fosgate's ownership of the Names and Goodwill.

         2.2      No Purchase of Other Assets. Other than the Assets, Rockford
                  will not acquire any other asset of Fosgate. Rockford
                  specifically acknowledges that it will not acquire any of
                  Fosgate's cash, accounts receivable, or other assets other
                  than the Names and Goodwill.

         2.3      No Assumption of Liabilities. Rockford will not assume any
                  liability in connection with this Agreement.

         2.4      Right of Repurchase. If Rockford ceases using the Names and
                  Goodwill for more than 2 years, and determines that it does
                  not intend to use the Names and Goodwill thereafter, then
                  Rockford shall offer to return the Names and Goodwill to
                  Fosgate without charge to Fosgate. Any return of the Names and
                  Goodwill to Fosgate will be made "as is" without any warranty.

                                      -3-
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3.       CLOSING. The Closing will take place at 10:00 A.M., local time, on or
         before September 30, 2000, at the offices of Steptoe & Johnson LLP,
         Counsel for the Rockford, 40 North Central Avenue, 24th Floor, Phoenix,
         Arizona 85004, or at another agreed upon time and place.

4.       PURCHASE PRICE. Rockford will, in full payment for the Assets, pay to
         Fosgate:

         4.1      Initial Price. $(Confidential Information redacted and filed
                  separately with the Commission.) payable by check at the
                  Closing, with one-half payable to James and Norma Fosgate and
                  one-half payable to Charles Wood.

         4.2      Royalty. A royalty for any product that Rockford sells after
                  the Closing Date and within (Confidential Information redacted
                  and filed separately with the Commission.) years after the
                  Closing Date using the name "Fosgate-Audionics," "Audionics"
                  or any other combination using a form of the name "Audionics"
                  (for example, "Rockford-Fosgate-Audionics" or "Hafler
                  Audionics").

                  (a)     Payments. The royalty will be paid in the amount of
                          (Confidential Information redacted and filed
                          separately with the Commission.) % of Rockford's net
                          sales of such products, with payments made quarterly
                          within 30 days after the end of each quarter. One-half
                          of the royalty is payable to Fosgate and one-half to
                          Charles Wood. Net sales equals the net invoice price
                          of products actually shipped to dealers, excluding
                          freight and duties but including allowances for
                          discounts, marketing and coop expenses, and returns.

                  (b)     Exclusion. Fosgate acknowledges that Rockford is
                          already the owner of the name "Rockford-Fosgate" and
                          that no royalty is due on any product using the name
                          "Rockford-Fosgate" or any variant or combination of
                          names so long as the variant or combination does not
                          include a form of the name "Audionics."

                  (c)     Right to Audit and Procedure.

                           (1)      Once per year, Fosgate may arrange to have
                                    an independent accountant audit Rockford's
                                    records relating to the sale of
                                    Fosgate-Audionics and Audionics branded
                                    products to confirm that the required
                                    royalty has been paid. Rockford will provide
                                    reasonable access to these records.

                           (2)      The auditor will report the results of its
                                    investigation to both Fosgate and Rockford.
                                    Rockford will have the right to dispute the
                                    auditor's findings by giving Fosgate notice
                                    within 60 days after Rockford receives them.
                                    If Rockford disputes the findings, Fosgate
                                    and Rockford will meet and attempt to
                                    resolve the dispute. If they are unable to
                                    do so, they will submit the matter to
                                    another independent auditor who is mutually
                                    acceptable to Fosgate and Rockford and the
                                    findings of this new auditor will be final.

                           (3)      If the auditor finds a shortfall in royalty
                                    payments of more than 5%, then Rockford will
                                    reimburse the costs of the audit(s). If the
                                    shortfall is less than 5% or if there is an
                                    excess payment, then Fosgate will bear the
                                    costs of the audit(s).

                                      -4-
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                           (4)      If the audit finds a shortfall in royalty
                                    payments, Rockford will pay the shortfall
                                    within 30 days after the final
                                    determination. If the audit finds excess
                                    royalties were paid, Rockford is entitled to
                                    offset the excess against future royalties
                                    until the excess is fully offset.

5.       REPRESENTATIONS AND WARRANTIES BY FOSGATE. Fosgate represents and
         warrants to Rockford as follows:

         5.1      Ownership of Assets. Fosgate is conveying the Assets "as is"
                  and makes no warranty as to Fosgate's title to or the
                  condition of the Assets.

         5.2      No Knowledge of Encumbrances. Fosgate does not know of any
                  assertion of an interest in or Encumbrance against the Assets
                  through or authorized by Fosgate.

         5.3      Harman Agreements. The copies of the Agreement between Fosgate
                  and Harman International, and of the letter signed by Harman
                  International, (each relating to Harman's transfer of the
                  Names and Goodwill to Fosgate) are true and correct copies of
                  documents Fosgate received from Harman and Fosgate believes
                  that they were signed by an authorized representative of
                  Harman.

         5.4      Binding Effect. This Agreement, and each other document
                  executed by Fosgate in connection with this Agreement,
                  constitutes Fosgate's valid, binding, and enforceable
                  obligation.

         5.5      Litigation.

                  (a)      There is no Proceeding pending or, to Fosgate's
                           knowledge, threatened; and

                  (b)      There is no Order in effect or, to Fosgate's
                           knowledge, threatened

                  against, relating to or adversely affecting Fosgate, the
                  Assets, or the transactions contemplated by this Agreement.
                  Fosgate does not know any basis for such a Proceeding or
                  Order.

         5.6      Bankruptcy Proceedings. Fosgate is not involved in any
                  Proceeding by or against it (a) under the Bankruptcy Code, (b)
                  under any other insolvency or debtors' relief Law, or (c) for
                  the appointment of a trustee, receiver, liquidator, assignee,
                  sequestrator or other similar official.

         5.7      No Employees. Fosgate does not have any employees whose
                  activities are related to the Assets.

6.       REPRESENTATIONS AND WARRANTIES BY ROCKFORD. Rockford represents and
         warrants to Fosgate as follows:

                                      -5-
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         6.1      Organization and Authority. Rockford is a corporation duly
                  organized, validly existing and in good standing under the
                  laws of Arizona and has all requisite power and authority to
                  enter into this Agreement and to carry out the transactions
                  contemplated by this Agreement.

         6.2      Binding Effect. This Agreement, and each document executed by
                  Rockford in connection with this Agreement, constitutes the
                  valid, binding, and enforceable obligation of Rockford.

         6.3      Execution, Delivery and Performance of Agreement. The
                  execution, delivery, and performance of this Agreement by
                  Rockford will not (with or without the giving of notice or the
                  passage of time) conflict with, result in a default under, or
                  result in the creation of any Encumbrance pursuant to, (a)
                  Rockford's articles of incorporation or bylaws; or (b) any
                  material Contract or Law to which Rockford is a party or by
                  which it may be bound.

7.       PRE-CLOSING COVENANTS. After the execution of this Agreement and before
         the Closing or termination of this Agreement:

         7.1      Consents and Approvals. Rockford and Fosgate will cooperate

                  (a)      to obtain as expeditiously as possible all material
                           Permits necessary to carry out the transactions
                           contemplated by this Agreement; and

                  (b)      to comply with all material Laws regulating or
                           restricting the transactions contemplated by this
                           Agreement.

         7.2      Approval of Certain Transactions. Fosgate will not, without
                  Rockford's prior written approval, take or agree to take any
                  of the following actions:

                  (a)      sell or otherwise dispose of any of the Assets;

                  (b)      incur any debt that encumbers the Assets; or

                  (c)      enter into or terminate any material Contract related
                           to the Assets.


         7.3      Asset Restrictions. Fosgate will take no action that would
                  encumber or restrict the Assets or their sale or transfer.

         7.4      Confidentiality. A party may make a public announcement of the
                  transactions contemplated in this Agreement only with the
                  prior written consent of all other parties. A party will not
                  unreasonably withhold consent if an announcement is required
                  by applicable securities laws.

                                      -6-
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8.       CONDITIONS TO ROCKFORD'S OBLIGATIONS. Rockford is not obligated to
         close the transactions contemplated by this Agreement unless the
         following conditions are satisfied on or before the Closing Date:

         8.1      Accuracy of Representations and Warranties. The
                  representations and warranties of Fosgate in Section 5 of this
                  Agreement must be true and correct, in all material respects,
                  both when made and on the Closing Date.

         8.2      Performance of Obligations and Delivery of Documents. Fosgate
                  must have performed all covenants, agreements, and obligations
                  required of them by this Agreement and must have delivered to
                  Rockford all documents required to be delivered at or prior to
                  the Closing.

9.       CONDITIONS TO FOSGATE'S OBLIGATIONS. Fosgate is not obligated to close
         the transactions contemplated by this Agreement unless the following
         conditions are satisfied on or before the Closing Date:

         9.1      Accuracy of Representations and Warranties. The
                  representations and warranties of Rockford in Section 6 of
                  this Agreement must be true and correct, in all material
                  respects, both when made and on the Closing Date.

         9.2      Performance of Obligations and Delivery of Documents. Rockford
                  must have performed all covenants, agreements, and obligations
                  required of it by this Agreement and must have delivered to
                  Fosgate all documents required to be delivered at or prior to
                  the Closing.

10.      OBLIGATIONS AT AND AFTER CLOSING.

         10.1     Fosgate Deliveries. At the Closing, Fosgate will deliver to
                  Rockford:

                  (a)      a bill of sale duly executed by Fosgate for transfer
                           of the Assets to Rockford or its nominees; and

                  (b)      all documents required to be delivered to Rockford
                           under this Agreement.

         10.2     Rockford Deliveries. At the Closing, Rockford will deliver to
                  Fosgate:

                  (a)      the Initial Price of $(Confidential Information
                           redacted and filed separately with the Commission.);
                           and

                  (b)      all documents required to be delivered to Fosgate
                           under this Agreement.

         10.3     Additional Documents. At and after the Closing, each party
                  will execute and deliver other documents and take further
                  action, as any other party reasonably deems necessary, to
                  carry out the transactions contemplated by this Agreement, to
                  effectively and irrevocably transfer the Assets to Rockford,
                  to confirm Rockford's title to the Assets, or to put Rockford
                  in possession and operating control of the Assets.


                                       -7-
<PAGE>   8
11.      TERMINATION.

         11.1     Rights to Terminate. A party may terminate this Agreement at
                  any time before the Closing:

                  (a)      by mutual written consent of Fosgate and Rockford;

                  (b)      by written notice to the other parties if the Closing
                           has not occurred on or before June 30, 2000; or

                  (c)      by written notice to the other parties if (1) a
                           material representation or warranty of the other
                           party was or has become inaccurate or untrue or (2)
                           the other party has failed to comply with or perform
                           under this Agreement (except that, if the
                           misrepresentation or breach is curable then this
                           Agreement will not terminate until the responsible
                           party has failed for 10 days after notice to cure the
                           misrepresentation or breach).

         11.2     Effect of Termination. If this Agreement is terminated, no
                  party will have any liability or further obligation unless the
                  termination was a result of such party's (a) breach, (b)
                  violation of its duties, obligations, representations, or
                  warranties, or (c) fraud, bad faith, or willful misconduct.
                  The Confidentiality Agreement will survive any termination and
                  govern the parties' obligations with respect to Information
                  and confidentiality.

12.      POST-CLOSING COVENANTS.

         12.1     Consulting Services. In connection with the development of its
                  business relating to the Assets after the Closing, Rockford
                  will have the right to call upon Jim Fosgate and Charles Wood
                  to provide limited public relations services (as mutually
                  agreed) relating to development of new products, and of a
                  distribution network for new products, to be sold under the
                  Names.

                  (a)      For up to five years after the Closing, Jim Fosgate
                           will make appearances at two mutually agreed trade
                           shows, press conferences, and other events, without
                           additional charge to Rockford other than the
                           royalties due under this Agreement and expenses paid
                           under (b) below.

                  (b)      To the extent such services require travel or other
                           expenses, Rockford will reimburse Jim Fosgate for
                           reasonable expenses so long as Rockford approves the
                           expenses in advance and is provided receipts.

         12.2     Limited Non-Compete. After the closing, Fosgate will not use
                  the Names, or any confusingly similar name (including the name
                  "Fosgate") in connection with any business or on any product
                  that is related in any way to the Business. This restriction
                  does not limit Fosgate's ability (a) to engage in the Business
                  using names that are

                                      -8-
<PAGE>   9
                  wholly distinct from the Names and from the name "Fosgate" or
                  (b) to use the name "Fosgate" in connection with the surround
                  sound processes Fosgate has licensed to Dolby Laboratories.

         12.3     Endorsement. For five years after the Closing, Jim Fosgate
                  will permit Rockford to use his name and likeness in
                  advertising and promotion of products that use the Names,
                  without compensation other than the Royalties payable under
                  this Agreement.

13.      NOTICES. Notices under this Agreement must be in writing. Notices are
         deemed given (a) when personally delivered, (b) when received by
         facsimile, electronic mail transmission or by overnight courier
         service, (c) on the fifth business day after mailing by first class
         registered mail, return receipt requested. Notices must be sent to the
         parties at the addresses stated on the signature page of this Agreement
         (or at any other address designated in a notice given by a party to
         change its address).

14.      CERTAIN COSTS.

         14.1     Costs of Proceedings. In any Proceeding arising under or
                  related to this Agreement the prevailing party is entitled, in
                  addition to other amounts it recovers, to have the other party
                  pay all costs and expenses (including reasonable attorneys'
                  fees) incurred in connection with the Proceeding.

         14.2     Expenses. Each party is solely responsible for its own
                  expenses relating to the preparation, execution, and
                  consummation of this Agreement and the transactions
                  contemplated by this Agreement.

         14.3     Broker's Fees. Each party is solely responsible for, and
                  indemnifies the other against, obligations to any broker,
                  finder or intermediary retained by it.

15.      MISCELLANEOUS.

         15.1     Integration and Amendment. This Agreement constitutes the
                  entire agreement of the parties, and supersedes all prior
                  agreements or understandings among the parties, with respect
                  to its subject matter. This Agreement may be amended only in a
                  written agreement signed by all of the parties.

         15.2     Waivers. No waiver under this Agreement is valid unless it is
                  in writing and signed by the party giving the waiver. A waiver
                  of a particular matter does not waive a subsequent or similar
                  matter.

         15.3     Binding Effect. This Agreement is binding upon, and inures to
                  the benefit of, each party and its successors and assigns.

         15.4     No Benefit to Others. This Agreement is solely for the benefit
                  of the parties (and their successors and assigns) and does not
                  confer any rights on any other persons except for Charles
                  Wood.

                                      -9-
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         15.5     Severability. The invalidity or unenforceability of any
                  provision of this Agreement does not affect the other
                  provisions. This Agreement is to be construed in all respects
                  as if it excluded any invalid or unenforceable provision.

         15.6     Construction and Headings. Whenever a singular word is used in
                  this Agreement it also includes the plural if required by the
                  context, and vice versa. Paragraph headings are for
                  convenience only and do not define or limit the contents of a
                  paragraph.

         15.7     Cooperation. In order to carry out this Agreement, each party
                  will cooperate, will take further action, and will execute and
                  deliver further documents as reasonably requested by any other
                  party.

         15.8     Counterparts. This Agreement may be executed in one or more
                  counterparts, all of which taken together are one original.

         15.9     Governing Law. This Agreement is governed by the internal Laws
                  of Arizona. Exclusive jurisdiction and venue for any
                  litigation arising under this Agreement is in the federal and
                  state courts of Maricopa County, Arizona.

16.      EFFECTIVE DATE. This Agreement is executed and effective as of
         9-21, 2000.

                                ROCKFORD CORPORATION, an Arizona corporation


                                By:  /s/ Gary Suttle
                                   --------------------------------------------
                                     President


                                By:  /s/ James M. Thomson
                                   --------------------------------------------
                                     Secretary

                                   Address: 546 South Rockford Drive,
                                     Tempe, Arizona  85281
                                     Attention:W. Gary Suttle, President
                                     Telephone  (480) 967-3565
                                     Facsimile  (480) 966-3639

                                FOSGATE

                                     /s James M. Fosgate
                                -----------------------------------------------
                                     James Fosgate


                                      -10-
<PAGE>   11
                                        /s/ Norma Fosgate
                                -----------------------------------------------
                                     Norma Fosgate

                                Address:
                                                 POB 564
                                                 Heber, UT 84032

                                        Telephone  (435)654-0248

                                        Facsimile  (435)654-0248

                                      -11-
<PAGE>   12

                                  Bill of Sale
                                       and
                               Conveyance of Names


            James and Norma Fosgate ("Fosgate") grant, sell, and convey to
Rockford Corporation ("Rockford") all of their interest in the Names and
Goodwill as defined in the Asset Purchase Agreement ("Agreement") between
Fosgate and Rockford.

            The Names and Goodwill are transferred to Rockford "as is" and
Fosgate makes no warranty as to Fosgate's title to or the condition of the Names
and Goodwill, except for those warranties expressly set forth in the Agreement.

            Dated and Effective as of 9-20, 2000.


                                               FOSGATE

                                               /s/ James Fosgate
                                               -----------------------------
                                                   James Fosgate

                                               /s/ Norma Fosgate
                                               -----------------------------
                                                   Norma Fosgate




Confidential Treatment Requested. Confidential portions of this document have
been redacted and have been separately filed with the Commission.