No idea. Find some benchmarks out there.
Just to note, my RAM is the same price (or cheaper counting shipping) and better than the two ares linked to, but his combos are great.
I would also consider the i5. Here's what it would look like:
CPU: i5-750 $200
Mobo: Asus P7P55D-E Pro
RAM: same as above
Total: $505. The board is quite a bit more expensive, but has USB 3/SATA III support even when Crossfiring, which others might not. There are several cheaper ones out there if that's above your budget.