That MOBO supports ATI CrossfireX. If I were you, and you wanted top-of-the-line, I'd get an HD5970 and an HD5870 for $400 less, which you can invest on liquid cooling if you wanted. Alternatively, $1,200 in 2x HD5970 would be beastly, and $200 could go into a Corsair 850Watt PSU.
ATI has terrible linux support which I need to dual boot. I have an ATI in work and know for years how difficult it is to get going on my unix box. So, I'll have to stick with Nvidia.