i dont think the problem is your graphics card at all. a single 6670 is more than capable to run 2 monitors at 1440p easily for work purpose.
hell even intels integreted graphics can run 2 monitors easily .
so i think the problem is something else .
not sure what but try to find out !!
Thanks..that's what I thought as well, then it occurred to me this morning, that I'm also running the Linux equivalent of Aero. That will consume cycles big time. Going to run a test with the eye-candy turned off, and see what happens.