How much are you paying for 2x7900GT's or for one 7900GTX? Anyway, you should bear in mind that when you're drooling over the next generation of cards (a lot sooner than you expect) it'll be more difficult to get rid of 2 cards than to upgrade just one. Or the single GTX can become a pair a little further down the road and then 2 GTX's will be better than 2 GT's