well i doubt you have a 680i mobo so you cant run sli effeciently enough to justify 2 cards. im betting you dont even have an sli mobo anyways if you have to ask.
ur psu wouldnt power it anyways.
so pickup a 8800 gts 320mb for 1280/1024 res and lower 640 for higher.
or wait for the 8800gt and 2950 pro in late november which you probably should, they will beat the 8800 gts series and be like 200-250$
I actually have a XFX LGA 775 NVIDIA nForce 680i SLI, and I don't have vista I have XP 32. I really don't want to wait till late november for it. I guess I'll purchase a new PSU along with the V/C.