My setup : Q6600 2.4Ghz quadcore + 8GB RAM, ATI 5850 , Monitor resolution: 1680x1050
Whenever i play BF3 on high setting at stock 2.4Ghz, i always got like 12FPS to 28FPS (64players map).After i overclocked cpu to 3.5Ghz, my FPS never drop below 20fps in 64 Players map( 22FPS to 44FPS) i think.
If you can, just overclock your cpu. Don't upgrade now because new intel processor will come out soon( Haswell). Or maybe you can wait for Broadwell= 2014.
We're talking 50->60 or more, you might as well go for it. Though i guess wait till June for Haswell? At least that's what i'm doing, i have a Core 2 Quad Q8400. Could only OC by 4%. But then my performance is as good as an A8-3570K, and you can see where that lies on the charts... http://www.tomshardware.com/reviews/cpu-performance-com...
Then of course:
This is single player:
I think it is worth the upgrade, because you get a overall platform upgrade too, faster performance everywhere, and games of course.
Though i'd still suggest waiting for Haswell. Probably be the last DDR3 desktop platform, the fastest DDR3 desktop platform (+10% over Ivy) and the most power efficient. Better QuickSync, more x86 extensions, etc.