Looks good but there's a couple of things I would change. I would buy G.Skill RAM rather than Corsair as timings don't matter on Sandy Bridge as much as frequency.
A different brand of GPU such as EVGA, msi, or ASUS, would also help. I've haven't had many good experiences with Palit so I suggest you choose a more 'reputable' brand. You would also do well in sticking with a GTX 570. In the below benchmark site, the GTX570 comes well above the 6970. PassMark Software - Video Card Benchmarks - High End Video Cards
I would definitely go with a Z68 chipset board. When it comes to motherboards, newer is almost always better. The Z68 chipset will be a much better option.
You probably won't need an 850w PSU. I would go with something like a Corsair HX750 which still gives you a fair bit of headroom for upgrades.
EDIT: Though the Enthusiast or TX series is still decent.