Yeah, I struggled with it for a while. Was stumped, really. With two 470s my framerates dropped to as low as 25 FPS in the middle of Zargabad. I couldn't turn without some absolutely awful stuttering on that map -- especially in the neighborhoods around the temple. This was especially true when there happened to be three or four attack helicopters overhead -- the Apaches, in particular. The Chinooks, too.
I tried everything that my friends over at the Arma website suggested: this and that driver, more RAM, no hyperthreading, install on an SSD, etc. Nothing worked. I gained a few FPS after the patch that included all the new memory allocators, though. My old rig got to as high as 80 FPS with the 470s and an i7 870, but the erratic framerates remained a constant source of frustration.
I'm sure you know how stunning the graphics on that game can be with AA, max or near max settings and smooth framerates -- almost photo-realistic at times. Once I experienced that game in its full, insane glory it became rather difficult for me to play on settings other than high to very high.

So it was a bit of a let down when I had to lower settings on my previous setup. But, alas, I couldn't hit a consistent 60 or even 55 FPs -- and that was on a 1680x1050 monitor (75Hz, though). Perhaps the stock i7 870 was the bottleneck?
So you play that game? Always glad to bump into fellow Arma players outside of the Arma websites.
I haven't tried the DayZ mod yet. I should.