Now a GTX in SLI will not work, this only has 2 PCI-E outputs. And I'd like to have faith in my system by getting something more powerful. They do make one like this in 620W instead of 520W, but I am settling for 520W
It will power an 8800GTS or GTX with ease. I would use the 620W version for SLI'd 8800GTSs any time, but even though it would handle it well, I'd probably buy a bigger unit for SLI'd GTXs. If you can afford to spend that much on two top-end video cards, and extra $50 for a Silverstone ST75ZF or Seasonic M12 700W shouldn't be a problem.