You might want to consider a GTX 560 Ti 448 core model and overclock it to GTX 570/480 levels.
This is very good advice.
Also, the 480 will achieve within a few % +/- of a GTX 570, so you can just find modern benchmark numbers on that card and then you more or less know how the 480 will do. I'm unaware of any game where there is a large difference between the two performance-wise. Dunno how much overclocking headroom the 480 has but I'd guess not too much.
The 570 is no doubt a better card, it's just not worth $370. IMO the 560ti 448 would be worth the $50 over the GTX 480 - you could overclock it to perform better than the 480/570 and you won't get the power/heat/noise issues.