Definitely not a GTX 580.
Reasons to go 7950: Low power consumption, it's out right now, should be fast enough
To wait: Kepler high-end will be faster, I'd expect the 670 to at least match ~7970 performance, prices should drop, but then again the high-end stuff isn't coming out for a while.
Waiting will bring lower prices, sure. I've seen a 6770 for $70 after rebate, there's VERY little downside to getting a 2nd one to Crossfire and using that for the next few months. I would be shocked if you can't sell that 6770 for at least $60 each.
Whatever you do, I'd recommend either going in on the 7000 series now/soon, or getting a cheap holdover, and upgrading to some next-gen stuff later. I personally hate getting stuck with last-gen stuff right before the new cards release
And whats with all this VRAM nonsense? I've seen benches of GTX 580 SLI, 1.5GB vs 3GB version, and no difference between the 2 at 1080p. 6770 CF might be similar to a 6970, which definitely doesn't need 2GB (see above). If 1.5GB is the magical cutoff between "slow" and "fast", I'd like to see some benches backing it up.
EDIT: Oh, for folding definitely go with Nvidia. I'd wait for Kepler.Edited by jrbroad77 - 2/29/12 at 2:45pm