If you are to only crossfire or SLI 2 medium end cards, I would suggest you to keep your CPU and your board. Can you do crossfire with your old board? Sincerely, if you don't put at least two 6950 together, the jump to intel will be a waste of money.
If you only got a single PCI-X slot, just go for a big card like a 6950 or even a GTX570.
I really think you are wasting your money by upgrading with the cpu you got. Just buy a aftermarket heat sink and OC that beast. These Phenom II are really good chips for OC. You can easily gain 15% with a good and cheap heatsink like a Cooler Master 212+.