i recommend a x1900xt/xtx... the is faster than a single 7800gtx 256, in just about every test, and the 1900xtx is faster than a gtx512 i believe, plus there not as rare and even cheaper if u can find one, but if u have somthing aganist ati then the 7800gtx512 will make u very happy, as long as you can find one... id recommend a single card over sli due to the fact that sli is unreliable, by this i mean in some games sli runs great, and in others its very slow for unknown reasons (bad drivers maybe? i duno) u can see this in hl2 the most i believe. plus sli is more or less in beta stages, things arnt guarenteed to run correctly..... this is simply what ive heard about them, im not saying sli is bad im just saying its a newer tech and we all know about new stuff, wait to buy till all the bugs are worked out... since its been a while since it was released it could be much more stable now... in certain games tho single 512 runs faster than sli 256