The games engine is very well optimised; and the game looks very, very good. Hardware needed to run this game was overhyped slightly before launch and the end result is that it will run flawlessly; I have an unlocked 6950 2gb; which gets similar results to a 6970 with a small overclock. You will get fantastic performance with that system lol. I also have a 2500k @4.6ghz so little under your spec on that too. Same amount/type of ram. I get between 38(under the most extreme conditions)-58 fps on all ultra settings with msaa which is a performance killer and imo doesnt look great at that resolution; take it off for a cleaner look and it will run from 55-65fps on my card. Bet you cant wait?! From the benchmarks I have seen, the 6970 runs the 580 reasonably close price/performance wise on BF3.
These should help:
6970 performance
crossfire 6970s 2600k
Enjoy your rig.