I just switched from 2x5770s to a 570 gtx sc. So far it's been great with the single card setup. I do plan on SLI'ing in the future when prices drop. The xfire setup I had worked really well, but I decided to go back to a single card setup because AMD's drivers were pretty inconsistent. One release would do really good, but the next would crash my system so I'd have to roll back. 1 card is less of a headache, and from my experience with SLI on an older build, nvidia's drivers have always been better for me.