Is This a Good gaming Rig? And what graphics cards should i use Sli or Crossfire?

your power supply is probably fine, though it depends what cards you plan to crossfire. as for wether to go crossfire or Sli, i would probably go with Ati, because they have the new 5000 series out with the Dx11 thats the best choice, however dont get 2 cards at the same time. just add the money you would spend on both cards and get one REALLY good card. 1 really good card can still outperform 2 lower quality cards in crossfre. also that way you still have the option of using your other video card slot when you decide to upgrade again.