Two ATI HD 5850s are definitely better than a single card in almost every game. To take advantage of two cards of this magnitude you almost have to turn up FSAA to 8x and AF to 16x as performance with 4x FSAA is nearly CPU limited on a Core i7 920. Turning up the image quality is a benefit everyone can appreciate as the games are not stressed by two cards at 4X at all. Performance in games increases 30-40% over a single card in every case except Batman Arkham Asylum which has issues running in Crossfire mode. The cost of two HD 5850s if you can find them is $540 on Newegg, meaning it is more expensive than a single HD 5870 but has higher performance and more image quality enhancing features like up to 16x FSAA native.



Link: Motherboards