I always run at 1920x1080, the benchmark is pretty intense though, with a helicopter flying around blowing up cars n stuff in a street, my fps ingame while driving around and stuff is much higher, and I put everything to the max on the benchmark, just for the sake of benching. Otherwise I'm fine with playing on settings a bit below maxed.
Hmmm. I seriously doubt your 945 is bottlenecking your 5870 though. And i didnt notice the part where you said the i7 was at 4 Ghz
. That could explain alot.