<PAGE>

                                 EXHIBIT 10.6


                            401 NORTH BROAD STREET
                          PHILADELPHIA, PENNSYLVANIA

                              AMENDMENT TO LEASE


     This AMENDMENT TO LEASE is made as of the 29th day of June, 2000, by and
between CALLOWHILL MANAGEMENT, INC., a Pennsylvania corporation, successor in
interest to BROAD AND NOBLE ASSOCIATES, INC., a Pennsylvania corporation, as
managing agent for 440 East 62nd Street Company, a Pennsylvania limited
partnership, having its principal office at 401 North Broad Street,
Philadelphia, Pennsylvania 19108 (collectively, "Landlord") and SUNGARD RECOVERY
SERVICES INC., successor in interest to SUNGARD SERVICES COMPANY, having its
principal office at 1285 Drummers Lane, Wayne, Pennsylvania 19087 ("Tenant").


                                  WITNESSETH

     A.   WHEREAS, Landlord and Tenant have entered into that certain Agreement
of Lease dated September 1, 1986 (the "Mezzanine Floor Lease") for, inter alia,
certain space on the Mezzanine floor (the "Mezzanine Floor Space") of that
certain building located at and known as 401 North Broad Street, Philadelphia,
Pennsylvania (the "Building"); and

     B.   WHEREAS, Landlord and Tenant have entered into that certain Agreement
of Lease dated April 12, 1984 (the "Sixth Floor Lease") for, inter alia, certain
space on the sixth (6th) floor (the "Sixth Floor Space") of the Building; and

     C.   WHEREAS, Landlord and Tenant have entered into that certain Amendment
to Lease dated October 1989 (the "Seventh Floor Lease") for, inter alia, certain
space on the seventh (7th) floor (the "Initial Seventh Floor Space") of the
Building; and

     D.   WHEREAS, Landlord and Tenant have entered into that certain Amendment
to Lease dated September 30, 1991 (the "Seventh Floor First Expansion Space
Lease") for, inter alia, certain other space on the seventh floor (7th) floor
("Seventh Floor First Expansion Space") of the Building; and

     E.   WHEREAS, Landlord and Tenant have entered into that certain Amendment
to Lease dated November 19, 1992 (the "Seventh Floor Second Expansion Space,
Seventh Floor Third Expansion Space and All Remaining Seventh Floor Space
Lease") for, inter alia, certain other space on the seventh (7th) floor
(individually, hereinafter called the "Seventh Floor Second Expansion Space"
"Seventh Floor Third Expansion Space" and the "All Remaining Seventh Floor
Space" and collectively, the Initial Seventh Floor Space, the Seventh Floor
First Expansion Space, the Seventh Floor Second Expansion Space, the Seventh
Floor Third Expansion Space and the All Remaining Seventh Floor Space are
hereinafter called the "Seventh Floor Space") of the Building; and
<PAGE>

     F.   WHEREAS, Landlord and Tenant have entered into that certain Amendment
to Lease dated November 22, 1996 (the "Suite 816 Lease") for, inter alia,
certain space on the eighth (8th) floor (the "Initial Eighth Floor Space") of
the Building; and

     G.   WHEREAS, Landlord and Tenant have entered into that certain Amendment
to Lease dated December 23, 1996 (the "Eighth Floor First Expansion Space and
the Eighth Floor Second Expansion Space Lease") for, inter alia, certain other
space on the eighth (8th) floor (individually, hereinafter called the "Eighth
Floor First Expansion Space" and the "Eighth Floor Second Expansion Space" and
collectively, the Initial Eighth Floor Space, the Eighth Floor First Expansion
Space and the Eighth Floor Second Expansion Space are hereinafter called the
"Eighth Floor Space"), of the Building; and

     H.   WHEREAS, Landlord and Tenant have entered into that certain Amendment
to Lease dated as of March 1997 (the "Tenth Floor First Expansion Space and the
Tenth Floor Second Expansion Space Lease") for, inter alia, certain space on the
tenth (10th) floor (the "Tenth Floor First Expansion Space" and the "Tenth Floor
Second Expansion Space") of the Building; and

     I.   WHEREAS, Landlord and Tenant have entered into that certain Amendment
to Leases dated as of June 9, 1999 (the "Tenth Floor Third Expansion Space and
the Mezzanine Expansion Space Lease") for, inter alia, certain space on the
tenth (10th) floor and the mezzanine floor of the Building, the exclusive use of
the transformer located on the tenth (10th) floor of the Building and the
removal by Landlord of asbestos and lead (individually, hereinafter called the
"Tenth Floor Third Expansion Space" and the "Mezzanine Expansion Space" and
collectively, the Tenth Floor First Expansion Space, the Tenth Floor Second
Expansion Space, the Tenth Floor Third Expansion Space and the Mezzanine
Expansion Space are called the "Tenth Floor Space"); and

     J.   WHEREAS, Landlord and Tenant further desire to amend the Lease to
provide, inter alia, certain space for Tenant on the eleventh (11th) floor and
the ninth (9th) floor of the Building, certain rights to use certain areas of
the fifth (5th) floor roof and the eleventh (11th) floor roof (collectively, the
"Eleventh Floor Space and the Ninth Floor Space"), certain renewal options and
certain repair, removal and maintenance obligations on the part of Landlord, all
as more fully set forth in this Amendment to Lease (the "Eleventh Floor and
Ninth Floor Lease").

The Mezzanine Lease, the Sixth Floor Lease, the Seventh Floor Lease, the Seventh
Floor First Expansion Space Lease and the Seventh Floor Second Expansion Space
Lease, the Seventh Floor Third Expansion Space and All Remaining Seventh Floor
Space Lease, the Suite 816 Lease, the Eighth Floor First Expansion Space and the
Eighth Floor Second Expansion Space Lease, the Tenth Floor First Expansion Space
and the Tenth Floor Second Expansion Space Lease, this Eleventh and Ninth Floor
Lease and the terms and conditions of this Amendment to Lease, together with all
exhibits, riders, letter agreements, amendments and modifications thereto are
hereinafter collectively called the "Leases".

The Mezzanine Floor Space, the Sixth Floor Space, the Seventh Floor Space, the
Eighth Floor Space, the Tenth Floor Space, the Eleventh Floor Space and the
Ninth Floor other areas used or occupied by Tenant pursuant to and under the
Lease are hereinafter collectively called the "Premises".



<PAGE>

                                    AGREEMENT

     NOW, THEREFORE, in consideration of the mutual agreements herein contained
and for other good and valuable consideration, the receipt and sufficiency of
which are hereby acknowledged, and intending to be legally bound hereby, the
parties hereto agree as follows:

1.   Expansion Space.
     ---------------

     A.   Landlord hereby leases to Tenant, and Tenant hereby hires from
Landlord the entire eleventh floor of the Building consisting of approximately
96,212 square feet of space located on the eleventh (11th) floor of the Building
(the "Eleventh Floor Space") as such space is more specifically shown by the
crosshatched markings on the eleventh (11th) floor plan which plan is attached
hereto and made a part hereof as Exhibit "A", for a term commencing as of the
date hereof and terminating at 11:59 o'clock eastern standard time on June 30,
2010 unless such term is sooner terminated or is extended as provided in the
Leases or by agreement of the parties hereto, their successors or assigns, all
on the same terms and conditions as are contained in the Leases except as may be
specifically modified by and as specifically set forth in this Amendment to
Lease (the "Eleventh Floor Term"). As of the date hereof, Tenant will have the
right to immediate occupancy, use and access to the Eleventh Floor Space and the
right to condition, improve, alter, modify, fixture, decorate and to do all
things necessary or desirable as Tenant may determine to the Eleventh Floor
Initial Space all in accordance with the terms and conditions of the Leases and
to the extent Landlord's approval is required for same, such approval shall not
be unreasonably withheld, conditioned or delayed and may not be withheld for any
reason for any condition, improvement, alteration, modification, fixturing or
decorating which Tenant has done or constructed or caused to be done or
constructed at any time elsewhere in the Building or the Premises under the
Leases.

     B.   Landlord hereby leases to Tenant, and Tenant hereby hires from
Landlord 41,475 square feet of space located on the ninth (9th) floor of the
Building (the "Ninth Floor Space") as such space is more specifically shown by
the crosshatched markings on the ninth (9th) floor plan, which plan is attached
hereto and made a pan hereof as Exhibit "B", for a term commencing January
1,2001 and terminating at 11:59 o'clock eastern standard time on June 30, 2010
unless such term is sooner terminated or is extended as provided in the Leases
or by agreement of the parties hereto, their successors or assigns, all on the
same terms and conditions as are contained in the Leases except as may be
specifically modified by and as specifically set forth in this Amendment to
Lease (the "Ninth Floor Term"). Tenant will have access to and the right to
condition, improve, alter, modify, fixture, decorate and to do all things
necessary or desirable as Tenant may determine to the Ninth Floor Space all in
accordance with the terms and conditions of the Leases and, to the extent that
Landlord's approval is required for same, such approval shall not be
unreasonably withheld, conditioned or delayed and may not be withheld for any
reason for any condition, improvement, alteration, modification, fixturing or
decorating which Tenant has done, constructed or caused to be done or
constructed at any time elsewhere in the Building or the Premises under the
Leases.

     2.   Extension of Term. Notwithstanding anything contained to the contrary
          -----------------
in the Leases, the term of the Leases for all Premises leased by Landlord to
Tenant pursuant to the Leases shall be renewed and extended for an additional
six (6) year term (the "Extended Term") until 11:59 p.m. eastern standard time
on June 30, 2010 (the "Extended Lease Termination Date") unless such term is
sooner terminated or is extended as provided in the Leases or by agreement of
the parties
<PAGE>

hereto, their successors or assigns, all on the same terms and conditions as are
contained in the Lease, including, without limitation, all renewal options and
rights of first refusal now or hereafter set forth in the Leases except as may
be specifically modified by and as specifically set forth in this Amendment to
Lease. The Eleventh Floor Team, the Ninth Floor Term and the Extended Term are
hereinafter sometimes collectively called the "Term".

3.   Basic Rent.
     ----------

     A.   Notwithstanding anything contained to the contrary in the Leases,
commencing July 1, 2000 (the "Extended Term Rent Commencement Date") Tenant
shall pay to Landlord, as basic rent payable during the Extended Term under the
Leases for all Premises leased pursuant to the Leases, (other than the Ninth
Floor Space and the Eleventh Floor Space for which the basic rent commencement
date shall be as set forth below in this Paragraph 3) the sum of Twelve Dollars
($12.00) per square foot of space leased pursuant to the Leases which space,
exclusive of the Ninth Floor Space and the Eleventh Floor Space, consists of
approximately 368,610 square feet. Tenant shall pay to Landlord, as and for
annual basic rent, an amount equal to the sum of Four Million Four Hundred
Twenty Three Thousand Three Hundred ($4,423,320.00) dollars, payable in equal
monthly installments, in advance, of Three Hundred Sixty Eight Thousand Six
Hundred Ten ($368,610.00) dollars per month.

     B.   Commencing July 1, 2000, Tenant shall pay to Landlord, as basic rent
payable during the Eleventh Floor Term the sum of Twelve Dollars ($12.00) per
square foot for one-half (1/2) of the Eleventh Floor Space leased during the
Eleventh Floor Term, consisting of approximately 50,000 square feet. Tenant
shall pay to Landlord, as and for annual basic rent, an amount equal to the sum
of Six Hundred Thousand ($600,000.00) dollars, payable in equal monthly
installments, in advance, of Fifty Thousand ($50,000.00) dollars per month.

     C.   Commencing January 1, 2001, Tenant shall pay to Landlord, as basic
rent payable during the Ninth Floor Term the sum of Twelve Dollars ($12.00) per
square foot for the Ninth Floor Space leased during the Ninth Floor Term which
space consists of approximately 41,475 square feet. Tenant shall pay to
Landlord, as and for annual basic rent, an amount equal to the sum of Four
Hundred Ninety Seven Thousand Seven Hundred ($497,700.00) dollars, payable in
equal monthly installments, in advance, of Forty One Thousand Four Hundred
Seventy Five ($41,475.00) dollars per month.

     D.   Commencing January 1, 2002, Tenant shall pay to Landlord, as basic
rent payable for the balance of the Eleventh Floor Space during the Eleventh
Floor Term the sum of Twelve Dollars ($12.00) per square foot which space
consists of approximately 46,212 square feet. Tenant shall pay to Landlord, as
and for annual basic rent, an amount equal to the sum of Five Hundred Fifty Four
Thousand Five Hundred Forty Four ($554,544.00) dollars, payable in equal monthly
installments, in advance, of Forty Six Thousand Two Hundred Twelve ($46,2l2.00)
dollars per month. It is the intention of Landlord and Tenant that no basic
rent, additional rent or other charges shall accrue or be payable by Tenant with
respect to the balance of the Eleventh Floor Space consisting of approximately
46,212 square feet Space until January 1, 2002, as more specifically set forth
in this Paragraph 3. D.
<PAGE>

4.   Operating Expenses.
     ------------------

     A.   With respect to the Eleventh Floor Initial Space only, Paragraphs 3(b)
and 3(c) of the Lease is hereby amended to provide that the Real Estate Taxes
and Base Operating Charges for the Eleventh Floor Initial Space shall be based
on the calendar year 2000. The percentage of increase in the Real Estate Taxes
and the percentage of increase in the Operating Costs over the base year
allocable to the Eleventh Floor Initial Space will be 3.87%. The method of
computation of the increases of the Real Estate Taxes and the Operating Costs
shall be the same as stated in Paragraphs 3(b) and 3(c) of the Lease.

     B.   With respect to the Ninth Floor Space only, Paragraphs 3(b) arid 3(c)
of the Lease is hereby amended to provide that the Real Estate Taxes and Base
Operating Charges for the Ninth Floor Space shall be based on the calendar year
2001. The percentage of increase in the Real Estate Taxes and the percentage of
increase in the Operating Costs over the base year allocable to the Ninth Floor
Space will be 3.21%. The method of computation of the increases of the Real
Estate Taxes and the Operating Costs shall be the same as stated in Paragraphs
3(b) and 3(c) of the Lease.

     C.   With respect to the Eleventh Floor Expansion Space only, Paragraphs
3(b) and 3(c) of the Lease is hereby amended to provide that the Real Estate
Taxes and Base Operating Charges for the Eleventh Floor Expansion Space shall be
based on the calendar year 2002. The percentage of increase in the Real Estate
Taxes and the percentage of increase in the Operating Costs over the base year
allocable to the Eleventh Floor Expansion Space will be 3.57%. The method of
computation of the increases of the Real Estate Taxes and the Operating Costs
shall be the same as stated in Paragraphs 3(b) and 3(c) of the Lease.

5.   Roof Areas. Tenant shall have the sole and exclusive right and privilege to
     ----------
use and occupy in common with Landlord such portions of the fifth (5th) floor
roof area and the eleventh (11th) floor roof area as Tenant may deem reasonably
necessary or desirable at no additional cost to Tenant where Tenant maintains
and operates any and all of its machinery, equipment, electrical, HVAC plumbing,
generator systems and the like. Landlord and Tenant are hereby granted access to
the eleventh (11th) floor roof area through the eleventh (11th) floor corridor
and stairwell as set forth on Exhibit "A" attached hereto and made a part hereof
provided such access shall be conducted in such a manner as to cause no
interference with Tenant or the conduct of Tenant's business.

6.   Repairs, Improvements and Maintenance.
     -------------------------------------

     A.   Landlord, at Landlord's sole cost and expense, shall be responsible
for and shall perform the following repairs, replacements, construction, work
and maintenance in the Building and the Premises all in accordance with the
following terms and conditions (collectively, "Repairs and Improvements").

     B.   Within 90 days of the date of this Amendment to Lease, Landlord at
Landlord's sole cost and expense, shall prepare or cause to be prepared and
submitted to Tenant for Tenant's approval, by a reputable, qualified contractor,
approved in writing as to scope of work and contractor, for the removal of all
asbestos, lead and lead paint and PCB ballast in (i) the entire Building in
accordance with all applicable federal, state and local statutes, laws,
ordinances, codes, rules, regulations, insurance requirements and time tables;
and (ii) the Eleventh Floor
<PAGE>

Space and the Ninth Floor Space to be completed prior to the date Landlord is
required to turn over such space to Tenant under the terms and conditions of
this Amendment to Lease. Within 15 days of the date such plan for asbestos, lead
and lead paint and PCB ballast removal is delivered to and approved by Tenant,
Landlord shall let such work for bid by contractors approved by Tenant and/or
Tenant's consulting engineer. Tenant shall have final approval of all final
plans, specifications and materials, and with respect to the lead and lead paint
removal from the Eleventh Floor Space and the Ninth Floor Space, the cost to
remove same, for such asbestos, lead and lead paint and PCB ballast removal and
such removal shall be completed by Landlord, at Landlord's sole cost and
expense, except with respect to the removal of the lead and lead paint which
shall be paid for by Tenant, upon completion of such removal and approval as to
the cost of same, as soon as practicable and in accordance with all applicable
federal, state and local statutes, laws, ordinances, codes, rules, regulations
and insurance requirements but in no event later than the date on which Landlord
is required to turn over to Tenant space under the Lease, it being understood
that time is of the essence. The asbestos, lead and lead paint PCB ballast
removal referred to herein is hereinafter referred to as the "Asbestos, Lead and
PCB Ballast Removal Work."

C. Within 90 days of the date of the Amendment to Lease, Landlord, at Landlord's
sole cost and expense, shall prepare or cause to be prepared and submitted to
Tenant for Tenants approval, by reputable, qualified contractors, comprehensive
plans and time tables for (i) the installation and maintenance of a fully
automatic fire pump to replace the existing manual fire pump; (ii) the
installation and maintenance of a Building security system which monitors
ingress, egress and access to and from the Building on a twenty-four (24) hour,
seven (7) day a week basis, which system shall include continuous video camera
monitoring and storage of video tapes in a safe, secure area for not less than
sixty (60) days; (iii) the repair and maintenance of the facade of the entire
Building, which shall be evidenced by a certification to Tenant by Landlord's
contractor that all repair and maintenance issues have been addressed and
corrected; and (iv) the replacement and/or modernization of elevators numbered 1
and 2 in the Building in accordance with the plans previously prepared by
Fairway Elevator Company, Inc. All Repairs and Improvements shall be performed
in a good and workmanlike manner, in accordance with all applicable federal,
state and local law, statutes, ordinances, codes, rules, regulations and
insurance requirements. All contracts for the Repairs and Improvements shall be
approved in writing by Tenant and Tenants agents and consultants shall have the
right to inspect all work as it progresses and to approve and/or disapprove
same.

7. Options to Renew. Tenant, upon not less than 180 days prior written notice in
   ----------------
each instance, shall have the option to renew the Leases for three (3)
additional terms (individually called the "First Option Term", the "Second
Option Term" and the "Third Option Term" and collectively called the "Option
Terms") of five years each. The terms and conditions of each Option Term shall
remain unchanged except that during the Option Terms Tenant shall pay annual
basic rent for the Premises as follows:

     A.   During the First Option Term, commencing July 1, 2010 and annually
thereafter until June 30, 2015, annual basic rent shall be equal to the sum of
Eighteen Dollars ($18.00) per square foot of Premises leased to Tenant by
Landlord pursuant to the Leases, as such square footage may be changed, amended,
modified, increased or decreased from time to time, and shall be payable, in
advance, in equal, consecutive, monthly installments.
<PAGE>

     B. Within 180 days prior to the commencement of the Second Option Term and
the Third Option Term, respectively, Landlord and Tenant shall agree on a new
annual basic rent for the Premises, which annual basic rent, if agreement is
reached, shall be the new annual basic rent for the entire term of the next
succeeding Option Term; provided, however, in no event shall (1) the per square
foot amount of annual basic rent during the Second Option Term exceed one
hundred twenty (120%) percent of the per square foot amount of annual basic rent
payable during the First Option Term; and (2) the per square foot amount of
annual basic rent during the Third Option Term exceed one hundred twenty (120%)
percent of the per square foot amount of annual basic rent payable during the
Second Option Term.

8. This Amendment to Lease, to the extent applicable, supercedes each and every
provision of the Leases which are inconsistent herewith and except as herein
expressly modified herein, all of the terms, covenants, and conditions of the
Lease are hereby ratified and shall remain in full force and affect.

     IN WITNESS WHEREOF, the parties hereto have duly executed this Amendment to
Lease as of the day and year first above written.


                             LANDLORD: CALLOWHILL MANAGEMENT INC. successor
                             in interest to BROAD AND NOBLE ASSOCIATES, INC.,
                             a Pennsylvania corporation

                               by:  /s/ Allan Stillman
                                    ----------------------------
                             title: President
                                    ---------------------------

                             attest:
                                    ---------------------------
                             title:
                                    ---------------------------
                                          (corporate seal)


                             TENANT: SUNGARD RECOVERY SERVICES INC., successor
                             in interest to SUNGARD SERVICES COMPANY,

                             a Pennsylvania corporation

                               by:  /s/ James C. Simmons
                                    -----------------------------
                             title: President
                                    ----------------------------

                            attest: /s/ Paul D. Loveland, Jr.
                                    ---------------------------
                             title: Assistant Controller
                                    ---------------------------
                                         (corporate seal)
<PAGE>

                            401 NORTH BROAD STREET
                          PHILADELPHIA, PENNSYLVANIA

                                  CONSENT TO
                              AMENDMENT TO LEASE

     The following parties hereby acknowledge, consent and agree to all of the
terms and conditions contained in that certain Amendment to Lease for 401 North
Broad Street, Philadelphia, PA, dated as of __________________, 2000 between
Callowhill Management, Inc., successor in interest to Broad end Noble
Associates, Inc., as Landlord, and SunGard Recovery Services, Inc., successor in
interest to SunGard Services Company, as Tenant, to which this Consent is
attached, for all purposes contained in the Leases, as that term is defined in
the attached Amendment to Lease, and for all purposes contained in each and
every Subordination, Non-Disturbance and Attornment Agreement, and all exhibits,
riders and amendments thereto, executed by any of the undersigned in favor of
Tenant.

OWNER AND MASTER LESSOR:
-----------------------

Gerald S Kaufman, Nominee for
Nathan P. Jacobs, Samuel A.
Seaver, Philip Kessler and
Arthur S. Mandelbaum


-------------------------------
Gerald S. Kaufman, Nominee

FIRST MORTGAGEE:
---------------

Orix Real Estate Capital Markets

By:                                         Attest:
   ----------------------------                    ------------------------
         Title:                                             Title:

MASTER LESSEE:
-------------

440 East 62nd Street Co., a
New York limited partnership,
by its sole general partner,
Allan Stillman


-------------------------------
Allan Stillman, General Partner

LEASEHOLD MORTGAGEE:
-------------------

Wells Fargo Bank

By:                                         Attest:
   ----------------------------                    ------------------------
         Title:                                          Title: