In raw performance, the Geforce 480 is the most powerful, but also uses the most power. The 570 is a balance of power and power usage. The 460 is low power usage but not as good performance. So I rank: 570 > 480 > 460.
buy an gtx 570 which is better then both cards the gtx 480 is not that good card it gets hottler earlier and its older tech then gtx 570 and the gtx 570 is one of the best cards for the price the gtx 570 can play mordern games at higher resolution with some aa witout a bit lag.
3. 460 (Except you're really looking to the features)
570 is about the same as 480. Maybe a bit slower but it's worth it to get a 570. 480 is a hot and inefficient card, so I don't recommend it. The 460 is slower than these and totally different class, so if you're not looking to the extra features that this one has, You'd better avoid it.