Quote Originally Posted by zalbard View Post
There is an important note in regards to stock cooler GTX480 vs 5870 comparison.
5870 can reach 1000MHz GPU clock fairly easily (with 40% fan speed or so), which improves the performance by 17.65% over the stock card. Since GTX480 is around 15-20% faster than stock 5870 and is not quite overclockable on stock cooling (92C in Crysis at sock clocks? 1GHz 5870 is running cooler than that for me...), it might be worth considering going 5870 instead.
Various sites have OC'ed GTX 480 to around 770mhz and report 10%'ish performance improvements, which is not too bad. Guru3D did 806 mhz and it increased performance by 15%.

But this is the absolute limit of this card, with voltage you should be able to go past 1000mhz in 5870 with a stock cooler. There's no way you are raising the voltage of GTX 480 with stock cooler.