I would guess that 700 Watt would be sufficient. I will tell you that I just tried two 8800GTS 512 G92 cards and I have a 620W supply and its on the line of not enough. I can play some older games. But when I tried COD4 my PC just shut off. So I'm saying 620W isn't enough. I'd go with 750+ if I were you, but my pockets may be deeper.