Here is some basic PSU info to research:
PSU 101 information
http://www.xcpus.com/forums/ca...ide-psu-101-102-a.html
PSU Buyers guide
http://www.xcpus.com/forums/ca...de-reference-list.html
Any on these will power your rig up. Not sure what your budget is, but a x1950xt will need some Amps on the 12V rail to operate correctly. The Corsair 450 PSU listed below, would be the minimum that I would get for your needs. There are others out there, but for the quality and price, it's hard to beat.
PSU - $100 shipped , hard to beat for this price.
Antec NeoPower NeoHE 550 ATX12V 550W Power Supply 100 - 240 V UL, CUL, TUV, CE, FCC, CCC, CB, C-tick ? Retail
http://www.newegg.com/Product/...x?Item=N82E16817103941
PSU - $130 shipped Nice a quiet and cheaper from OEM, not from newegg.
ULTRA-QUIET PSU: SILENCER® 610 EPS12V
http://www.pcpower.com/product...roduct.php?show=S61EPS
PSU - $75 shipped - $20 MIR = $55! Can run a single 8800gtx system.
CORSAIR CMPSU-450VX 450W Active Power Supply Retail ***Free Shipping***
http://www.zipzoomfly.com/jsp/...p?ProductCode=10006428
PSU - $100 shipped - $10 MIR = $90! Good solid PSU for the $, hard to beat.
Corsair 520W SLI Certified Modular ATX Power Supply - CMPSU-520HX
http://www.buy.com/prod/corsai...loc/101/203270716.html
Hey first post! At least here, too many on others to care to list