I'm running an identical setup to the one you described except with a 285 (also on 2x 1900x1200 displays). I have the CPU overlocked a bit at 3.7 but aside from that nothing special. I played with the 5870 for a week or so and really didn't notice much difference (maybe 5-10% in Dalaran only), leading me to believe that at this point the CPU is the limiting factor. If there is anything else you would like me to check out let me know, I shouldn't have trouble finding another 5870 to test with.
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