Looking to upgrade my notebook: CPU or GPU more beneficial?

Nearly a year ago I bought a Dell E1705 as a budget gaming laptop for myself. It works well for most games, but I'm starting to notice reasonable performance drops on newer titles (COD4, UT3, GOW) and I'm considering a hardware upgrade. Here is my current configuration:

Intel Core 2 Duo T5200 (1.60ghz, 533mhz FSB)
2gb DDR2 533mhz
Geforce Go 7900gs 256mb (OC 500mhz/1100mhz)
WD 320gb SATA2
Windows XP x64/Vista Ultimate x86

My question is, what would be a better upgrade in terms of gaming performance?

Geforce Go 7950 GTX 512mb <--- The best card available for my laptop
Intel Core 2 Duo T7500 (2.2ghz) <--- Seems to be the best price/performance ratio

This is my first post here, so I'm eager to see what you all have to say

Yes, I figured someone would say that. Unfortunately buying a new laptop is kinda out of the question at the moment, plus the only single mobile graphics card better than the 7950 GTX is the 8800m GTX, which is only available in a couple super high end laptops as far as I know. So I'll just upgrade my graphics card, as I figured I should do in the first place. It still seems likely to me that my slower cpu could be acting as a bottleneck, but probably not as much as my GPU. Thanks for your input.