Umm I'm almost 100% sure that heat and noise wise 1 480 alone would probably come close to 3 260s.
I think if ur worried about heat and noise a 5870 would be better. Cheaper too, but if noise doesn't bother u and heat also,and u want more power than the 480 is ur beast
when I went from 3 285s to 1 5870 the min frame rate was way better even though the act frame rate was lower. Try to stick to 2 cards max.
did you run 3 gtx 285 with your i7 920 @ 4.02 GHZ? or you had other CPU?