How good of a graphics card can I upgrade to before my cpu starts to limit it?
I have a core i5 2320 at 3.0 ghz. I usually upgrade my gpu every year, to one under 150w and under $250. Right now I have a gtx 660.
More aboutupgrading question
You could go up to pretty much anything. You might have a slight drop off at the 670, 7970 or 680 but they'd still give an increase over they're lower models. Also I believe there is a way to keep the boost at 3.3Ghz regardless of usage.
The Core i5-2xxx is such a strong CPU, that you can choose any gfx card you can afford and not be hindered by CPU bottle neck... at least not enough to worry about.