<PAGE>   1
                                                                   EXHIBIT 10.11







                                  AMENDMENT TO
                    SECURED DEMAND NOTE COLLATERAL AGREEMENT











                              --------------------

                                   FORM SDN-A

                              --------------------














                NATIONAL ASSOCIATION OF SECURITIES DEALERS, INC.
                  1735 K STREET, N.W., WASHINGTON, D.C. 20006
<PAGE>   2
                                      NASD

                              SECURED DEMAND NOTE
                              COLLATERAL AGREEMENT
                     AMENDMENT EXTENDING THE MATURITY DATE

                                     SDN-A

                                    BETWEEN:

LENDER                  Summit Group of Companies Inc.
      --------------------------------------------------------------------------
                                        (NAME)

              25 Fifth Ave.
--------------------------------------------------------------------------------
                                (STREET ADDRESS)

         Indialantic                         FL                      32903
-----------------------------         -----------------         ----------------
           (CITY)                          (STATE)                    (ZIP)



                                      AND


BROKER-DEALER                 Summit Brokerage Services Inc.
             -------------------------------------------------------------------
                                           (NAME)

              25 Fifth Ave.
--------------------------------------------------------------------------------
                                (STREET ADDRESS)

        Indialantic                          FL                      32903
-----------------------------         -----------------         ----------------
           (CITY)                          (STATE)                    (ZIP)

NASD ID NO: 034643
           ---------------------------------------------------------------------

DATE FILED: 3/20/01
           ---------------------------------------------------------------------


<PAGE>   3
                                      NASD

                    SECURED DEMAND NOTE COLLATERAL AGREEMENT
                     AMENDMENT EXTENDING THE MATURITY DATE


     AGREEMENT dated 3/20/01 to be effective 5/1/01 between Summit Group of
Companies Inc (the "Lender") and Summit Brokerage Services, Inc. (the
"Broker-Dealer").

     In consideration of the sum of $40,000 (the unpaid principal amount) and
subject to the terms and conditions set forth in the Subordination Agreement
approved by the National Association of Securities Dealers, Inc., scheduled to
mature on 4/30/01 bearing the Loan Number 07-D-SDN-10286, the Broker-Dealer and
the Lender agree to extend the maturity date of the Agreement and Secured Demand
Note until 4/30/02. This amendment shall not become effective unless and until
the NASD has found the Amendment acceptable.

     If applicable, the interest rate on this Subordination Agreement is changed
from _______________ to ____________ percent per annum, effective as of the date
of this Amendment.

     IN WITNESS WHEREOF the parties have set their hands and seal this 23rd day
of March 2001.



                                             Summit Brokerage Services, Inc.
                                             -----------------------------------
                                             (Name of Broker-Dealer)



                                           By /s/ Mark F. Caulfield, CFO    L.S.
                                              ----------------------------------
                                              Mark F. Caulfield, CFO
                                              (Authorized Person)



                                              /s/ Richard Parker            L.S.
                                              ----------------------------------
                                              Richard Parker, CEO
                                              Summit Group of Companies Inc
                                              (Lender)



                                           FOR NASD USE ONLY


                                           ACCEPTED:
                                                    ---------------------------
                                                              (Name)


                                                    ---------------------------
                                                              (Title)

                                           EFFECTIVE DATE:
                                                          ---------------------

                                           LOAN NUMBER:
                                                       ------------------------
<PAGE>   4
                          SUBORDINATED LOAN AGREEMENT
                              LENDER'S ATTESTATION

         It is recommended that you discuss the merits of this investment with
an attorney, accountant or some other person who has knowledge and experience
in financial and business matters prior to executing this Agreement.

         1.       I have received and reviewed a copy of Appendix D of 17 CFR
                  240.15c3-1, and am familiar with its provisions.

         2.       I am aware that the funds or securities subject to this
                  Agreement are not covered by the Securities Investor
                  Protection Act of 1970.

         3.       I understand that I will be furnished financial statements
                  pursuant to SEC Rule 17a-5(c).

         4.       On the date this Agreement was entered into, the
                  broker-dealer carried funds or securities for my account.
                  (State Yes or No) Yes
                                   -----

         5.       Lender's business relationship to the broker-dealer is:
                  Affiliated Corporation -- 100% Owned By Broker/Dealer's
                  --------------------------------------------------------------
                  Majority Shareholder.
                  --------------------------------------------------------------

         6.       If not a partner or stockholder actively engaged in the
                  business of the broker-dealer, acknowledge receipt of the
                  following:
                            ----------------------------------------------------

                  --------------------------------------------------------------

                  a.       Certified audit and accountant's certificate dated
                           12/31/00
                           -----------------------------------------------------

                  b.       Disclosure of financial and/or operational problems
                           since the last certified audit which required
                           reporting pursuant to SEC Rule 17a-11. (If no such
                           reporting was required, state "none") None
                                                                ----------------

                           -----------------------------------------------------

                  c.       Balance sheet and statement of ownership equity dated
                           12/31/00
                           -----------------------------------------------------

                  d.       Most recent computation of net capital and aggregate
                           indebtedness or aggregate ___________ debit items
                           dated 12/31/00 reflecting a net capital of $74,254
                                 --------                             -------
                           and a ratio of 706%
                                         ---------------------------------------

                  e.       Debt/equity ratio as of 12/31/00 of 8%
                                                   --------    -----------------

                  f.       Other disclosures: None
                                             -----------------------------------

Dated: 3/23/01                            /s/ Richard Parker                L.S.
      -------------------        -----------------------------------------------
                                                    (LENDER)
                                         Summit Group of Companies, Inc.
                                              Richard Parker, CEO
<PAGE>   5

[LETTERHEAD]


March 30, 2001                                        BD# 34643

Mark R. Caulfield
Summit Brokerage Services, Inc.
25 Fifth Avenue
Indialantic, Florida 32903

Re:      Subordinated Loan Agreement Maturity Date Extension
Control #: 07-D-SDN-10286
Lender: Summit Group of Companies, Inc.
Amount: $40,000.00

Dear Mr. Caulfield:

The amendment extending the maturity date of the above referenced agreement
from April 30, 2001 to April 30, 2002 is accepted by the NASD Regulation, Inc.

It is important to note that the limitations required by paragraph V, which
covers permissive prepayments, will run from the effective date of the original
agreement, not from the date of this amendment.

If you have any questions regarding this Agreement or our acceptance thereof,
please contact me at (404) 239-6150.

Sincerely,


/s/ Nancy P. Mills/SLS
---------------------------
Nancy P. Mills
Supervisor of Examiners

/pag