Hi
You need to think off about going on for the latest supervisor modules in the 6500 switch if possible with redudant supervisor modules.
Also do check this data sheet of 6500 which clearly talks about different chassis and the gig and ethernet ports they can support.
http://cisco.com/en/US/products/hw/switches/ps708/products_data_sheet09186a00800ff916.html
Following are the services modules which can fit onto 6500 series switches..
. Content services gateway
· CSM
· Firewall module
· IDS module
· IP Security (IPSec) VPN module
· Network analysis module
· Persistent storage device
· SSL module
· Wireless LAN services module
http://cisco.com/en/US/products/hw/switches/ps708/products_data_sheets_list.html
above mentioned link contains the details about the power supply , transceiver , WAN , IOS , CAT OS which you can choose off for 6500.
Also make sure about the fan tray , off late there has been some compatible issue in normal and high speed fan trays which makes your SUP 720 to go off in sleep mode.
regds