Best gfx for E8600 @ 4.33 ghz

[hippie]

Hey guys, with battlefield 3 looming i am thinking about spiceing up my rig a bit.

Currently have a gtx280 running alongside my E8600 which is overclocked to 4.33 ghz.

I am not sure how best to improve this. A gtx 560 seems like an obvious choice, but will it be much better than the 280?

A 580 would be over kill for my processor?


I am not going to have enough room for sli/x-fire.

 

[hippie]

This is exactly what i was thinking, maybey stick a core 2 quad in there with a 560. But with that sort of money i could get an i5 bundle.