well it depends on the game you are playing. if I am not mistaken, Wow does not utilize SLI/crossfire(dual video cards) so it only uses 1 card. But most modern games have SLI/crossfire support(crysis, world at war, etc)

if you were thinking about getting 2 video cards, you can get the motherboard that supports crossfire(i.e 2 PCIexpress slots) and just get the 1 video card for now and get another video card at a later date

But I am curious at what other people would choose seeing as i never went crossfire or even used a ATI card. i know Wow had ATI problems and what not, but not sure if they are resolved.