Significant fps increase?

How many fps in games more would I get if I overclocked my 2500+ at 2080mhz to 3200+ speeds?

Right now I'm playing Unreal 2, could I get it to run smoother with that extra 120mhz, or is it mostly dependant upon my 9500 pro (351/317)?

IMHO, there will be little difference except if you up the fsb to 400+ and around 2400mhz for your cpu.
I think OCing your Radeon9500Pro might give you more juice.