Make sure you pick up a B3 version
of the motherboard to resolve the Sandybridge SATA2 connector issue.
I'd go for the 6950 personally; I like HIS versions of ATI cards. The GPU charts
will help you understand the performance difference. You'll just need to decide how much you want to spend.
Think everything else will be fine. That's a very good PSU but if you were considering crossfiring or using SLI in the future it may be a little underpowered.