I run dual GTX 660's in SLI to feed my U3011. Don't think I'd like going with a single GTX660 at this resolution.
You have to run two of those? I have a single Radeon HD 7850 that feeds my dual ASUS PB278Q's without a problem. Sure, they're diagonally 3" smaller, and 1360 pixels shorter, but the pixel-per-inch is higher (which is my rule for buying new monitors: same, if not better, pixel-per-inch). I'm surprised my quad stand (rated for ~24") can handle those honkers...
"It's in hyperspace . . . Gaia was once in real space, but it was so disgusted at the crimes and stupidities of human beings that, out of shame, it left space and refused to have anything more to do with the human beings it had sent out into the Galaxy." - a Sayshell University receptionist, Foundation's Edge, Isaac Asimov