I'd reccomend going with two GTX460s... two SLI GTX460s actually perform better than a GTX480... and they dont run so damn hot. Also, two GTX460's will actually use slightly les power than a GTX480 and cost about $100 less, so that power supply will still be fine with them.
I'd get two 1gb Gtx460s... or you could go with the 896mb superclocked versions.
Here's some hard data to support this http://www.fudzilla.com/reviews/reviews/reviews/evga-gt...
I'd reccomend a Hyper 212+ cooler. It's actually one of the best for i7's, and its only $40 bucks.