Go with the 6950. SLI/Crossfire is only worth it for the very top end cards. Period. Take it from someone who's addicted to SLI/Xfire
Secondly, get the core i5 2500K. For gaming, it's MUCH better than the AMD.
Thirdly, sapphire is fine, msi is fine. Everything is ok except for XFX. I wouldn't buy from them ever, they are a cheaper manufacturer with higher failure rates and very bad RMA process. At least according to people's experience on the Hard forum.