I just replaced my crossfired HD6950s for SLI'd gtx 680's and haven't been happier. I know it's a bit pricier, however I'd rather spend the extra dollar on cards that will have consistant drivers, and will run the game smoothly.
I've been playing fps games for 11 years and one thing I have stuck by is that the frame rates for optimum gameplay are above 65fps. And I think I've put in enough time to prefer maximum settings for todd frame rates. So if you're wondering what is best, just beef it up with what ever feels best
All being said, and all benchmarks aside, SOE won't produce a product thatll only be playable on one of two cards. It's poor marketing.
It'll run great if you have a beefy system, and run (ok) on a mediocre system.
Before you guys argue over hypetethetical conclusions based of technical aspects of how physX runs, I'd suggest jus waiting to see how the game operates. That way you spend less time guessing
Thanks Goku for the information!