I found a comprehensive review of 660 (SLI, up to 3-way), 670 and 680s.
http://uk.hardware.info/reviews/3026/nv ... i-included
So it appears doing a 660 SLI is going to help you right now (for $100 more than a single 680). On a single 1080 monitor on BF3 this will get you an additional 30-40 frames. SLI 670s get you 40-50, and SLI 680s get you 50-60 more. I think at this time a SLI 660 is a reasonable choice for $100 more than a single 680.
How long do you guys think a x60 card in SLI last compared to a single x80 card?
@Cella: I'll shoot you a PM. My question is relatively short, not deserving of a thread.
@BackDraft: I got a Antec 620 for $35 on special, and I get a reasonable 4.3 (vcore/temps). I ask about water cooling gpus because I am considering stepping up a bit more (after finding that I can push my chip to 4.7+, but it ran too hot so I need more cooling). I've seen these custom mounts that people are making to allow you to put closed loops on gpus.