Well this is an interesting situation.
By the numbers you posted, it seems that your CPU is able to go above 60FPS, so it's not your CPU that is limiting your system, it's the 660. BF3 is great with SLI, so you should get almost double FPS, I would estimate 75fps on ultra settings. But this is the point where your CPU might choke. Your best bet is more graphics power, then upgrade your CPU if it's at 100% usage.
I can't recommend SLI as I've had bad experiences. I used to have 2 x 560ti's and BF3 was choppy as hell. Went back to one and it was perfectly fine. I hope these issues don't affect you.