Go nvidia. I've got GTX470. The GTX560 is about the same performance as mine. And the GTX560Ti is even a bit better then mine. And I'm VERY happy with mine. Play every game @ 60fps with everything maxed out. (Flight Simulator X = 35-40fps all maxed out and prolly a few other games, but NEVER lower than 35fps, and I mean REALLY never (--> with my i7 proc, not with my Q9450 proc, since I can't see what hardware you have... Maybe put it in your sig?
2 nvidia cards (same model) = SLi
2 ATi cards (same model) = CrossFire
You cannot mix an nvidia with an ATi for SLi or CF setup.
You cannot SLi if you have 2 nvidia cards (different models)
You cannot CF if you have 2 ATI cards (different models)
2 nvidia cards (1 ASUS, 1 ZOTAC) will work in SLi (if they are the same model)
You CAN use 2 nvidia cards (different models) but not in SLi. Just put best as Primary and the other as dedicated Physx (requires to be at least 8800 series)
etc...Edited by ASUSfreak - 10/3/11 at 2:06am