The GTX 670 is the best card for it's price and performs better than the GTX 580 (even though you're talking about a GTX 570).
Tom's Hardware's article GeForce GTX 670 2 GB Review: Is It Already Time To Forget GTX 680?
Maybe this time will be different and we’ll see GeForce GTX 670s in sufficient quantity to satisfy the folks previously priced out of the ultra-high-end market. If that’s the case, then hell yes. GeForce GTX 670 is a phenomenal little board that blows right past the GeForce GTX 580—a card that was introduced at $500 a year and a half ago. It offers the display connectivity to contend with Eyefinity, one of AMD’s prior differentiators, and its efficiency is currently unmatched. We have every reason to recommend buying a GeForce GTX 670—even as an alternative to the GeForce GTX 680, which is marginally faster, but 25% more expensive.
Your better off returning your GTX 570.