Matters what resolution your playing, and how hard your pushing the video card.
http://www23.tomshardware.com/graphics_sli2007.html?modelx=33&model1=812&model2=819&chart=356
http://www23.tomshardware.com/graphics_2007.html?modelx=33&model1=740&model2=722&chart=296
You might want to start with one 8800GTX and add another one when nessessary.
SATA IDE 3.5 HARD DISK DRIVE COOLING COOLER DUAL FAN PC, BSTAR 650 Watt Dual Fan ATX 650W Gold SATA Power Supply, NEW 600W 20/24 pin Dual-Fan ATX PSU SATA Power Supply, Blue Star 450W 20+4pin Dual Fan ATX Power Supply w/SATA, Blue Star 580W 20+4pin Dual-Fan ATX Power Supply w/SATA, GD 650w ATX SATA AMD/P4 Dual Fan Power Supply 20-24 Pin, NEW 600W 20/24 pin Dual-Fan ATX PSU SATA Power Supply, SATA IDE 3.5 HARD DISK DRIVE COOLING COOLER DUAL FAN PC, GD 650w ATX SATA AMD/P4 Dual Fan Power Supply 20-24 Pin, Dual fan 600 Watt ATX Power Supply SATA Silent Intel KT PCI-Express, Gold Blue Star ES-650-GD 20+4-pin Dual-Fan 650W ATX PSU W/SATA, BSTAR 650 Watt Dual Fan ATX 650W Gold SATA Power Supply, Dual Hard Disk Cooling Fan for SATA IDE HDD PC Hard Drive with Mounting Screws, Blue Star 550W 20+4-pin Dual-Fan ATX Power Supply with SATA, Blue Star ES-550-D-Blue Star 550W 20+4-pin Dual-Fan ATX Power Supply w/SATA - Ki, SATA IDE 3.5 HARD DISK DRIVE COOLING COOLER DUAL FAN PC, 550 W Watt 20+4-pin Dual-Fan ATX Power Supply w/SATA, PoWork 650W 20+4-pin Dual-Fan ATX Power Supply w/SATA &, A-Power 450W 20+4-pin Dual-Fan ATX Power Supply w/SATA & PCIe, NEW Enlight 430W ATX 12V Dual-Rail 80mm Cooling Fan 4x SATA PCIe PC Power Supply, Dual Hard Disk Cooling Fan for Sata Hard Drive HDD IDE, Hercules Black ATX Dual Fan 600W Silent Power Supply PSU w/20-24pin SATA PCI-E, A Power APVA600-A-Power 600W 20+4-pin Dual-Fan ATX Power Supply w/SATA & PCIe - , 2U Style 575W Dual FanPCI-E SATA PSU 8 x Bay Rack Mount 5 x Fans EATX Case NEW, A-Power 600W 20+4-Pin Dual-Fan Atx Power Supply with Sata and PCIe , NEW 600W 20/24 pin Dual-Fan ATX PSU SATA Power Supply, NEW 600W 20/24 pin Dual-Fan ATX PSU SATA Power Supply, New 600W 20+4 pin Dual-Fan ATX Power Supply PCI-E SATA I5/I7 , A-Power 600W 20+4-pin Dual-Fan ATX Power Supply w/SATA, GenMax 480W 20+4-pin Dual-Fan ATX PSU w/SATA & PCIe (Black), A-Power 600W 20+4-pin Dual-Fan ATX Power Supply w/SATA & PCIe Connectors, NEW 680W 20/24 pin Dual-Fan ATX PSU SATA Power Supply, A-Power APVA450 20+4-pin Dual-Fan 450W ATX PSU W/SATA & PCIe, A-Power APVA600 20+4-pin Dual-Fan 600W ATX Power Supply W/PCIe & SATA, Blue Star 550W 20+4-pin Dual-Fan ATX Power Supply SATA, New 600W 20+4-pin Dual-Fan ATX PSU w/SATA P4/Vista, NEW 680W 20/24 pin Dual-Fan ATX PSU SATA Power Supply, New 600W 20+4-pin Dual-Fan ATX PSU w/SATA P4/Vista, A Power AGS620-A-Power AGS 620W 20+4-pin Dual-Fan ATX Power Supply w/SATA - Kit, A-Power APVA600 600W Watt ATX Computer Power Supply Dual Fan SATA PCIe, Free S/H 4U Rackmount Chassis (m)ATX D:15.8" Case w/ Dual Fan 480W SATA PSU NEW, A-Power APVA600 600W Watt ATX Computer Power Supply Dual Fan SATA PCIe, A-Power Ags 620W 20+4-Pin Dual-Fan Atx Power Supply with Sata , SATA IDE 3.5 HARD DISK DRIVE COOLING COOLER DUAL FAN PC, A-Power AGS6250 AGS 20+4-pin 620W Dual-Fan ATX PSU 110V 220V W/SATA, A-Power AGS 620W 20+4-pin Dual-Fan ATX Power Supply w/SATA - NEW, For PC SATA IDE Hard Disk Drive Cooling HDD Dual Cooler Fan in 1 Replacement, 3.5" Inch Dual Cooling Fan Hard Disk Driver HDD Cooler for PC SATA IDE 10.05CFM, Startech Dual 3.5in USB 3.0 Hot Swap Trayless SATA Hard Drive Enclosure W/ Fan, OKIA 550W Dual Fan ATX PC Power Supply 20-24pin SATA 6-Pin & 8-Pin--Brand NEW,
