I have an 8600gt and a 1.6 ghz e2140 dual core processor, will i get better frame rates if i have e8500 3.1ghz?

I have the above mentioned processor, and the 8600gt is the best card I can get for my system, and I was wondering how much FPS increase i would get for games like COD4, Bioshock, and source games if i went to an e8500 processor, 3.16ghz 1333 MHz FSB, 6mb L2 cache, from a 1.6 ghz processor with 800mhz FSB and 1mb L2 cache. Thanks!