Well, my GTX 465 flashed to a "470" has a 604,919 RAC (a major OC of coarse) so I am guessing you would do well a single card for now. If I am reading this chart correctly
https://spreadsheets.google.com/ccc?...CIyG89sF#gid=0 you would get slightly better credits (and less power usage and heat) out of a GTX 570 over a GTX 480 or dual 460s. Hope that is helpful.