Go with a 6800 hands down. Here's my system
3200+ XP with 400 Mhz FSB
1 GB DDR Ram
SB Live!
Windows XP Home
450W Power Supply
Originally I had a ATI Radeon 8500. It was able to score a measly 92 in 3D Mark 2003, and could play some older games life Counterstrike and such. Upgraded to an ATI X800 and I wasn't too happy. Out of the box it scored a 6700 on 3D Mark 2003 and choked up on Doom 3 and Far Cry. I returned it for a 6800GT. Out of the box scored a 11,000 in 3D Mark 2K3 and i'm playing Doom 3 at 1024x786, Ultra Deatil, 8X FSAA, and 16X filtering with no problems at all. Very pleased with this card, will def. be buying Nvidia in the future...