Best bang for buck gpu and cpu upgrade?

hi there been out of the upgrade game for some while having put together my system 2 years ago and coasted a bit, not really paying attention to the advances etc

now looking for my best bang for buck upgrade for around £300

Current setup is

Intel Core 2 Duo E6550 "LGA775 Conroe" 2.33GHz (1333FSB) - Retail

Leadtek GeForce 8800 GTS 640MB GDDR3 HDTV/Dual DVI (PCI-Express)

Corsair HX 620W ATX Modular SLI Compliant Power Supply (CMPSU-620HXUK)

Antec 900 Nine Hundred Ultimate Gaming Case - Black


Thermalright Ultra-120 Extreme CPU Cooler (Socket AM2/LGA775)

Abit IP35 Pro (Socket 775) PCI-Express DDR2 Motherboard

GeIL Black Dragon 2GB (2x1GB) PC2-8500C5 1066MHz DDR2 Dual Channel (GB22GB8500C5DC)


With that cooler I have got the CPU running at 3.10GHZ no problems so my question is what would be the best cpu and gpu upgrade I could make for around that price?

So far I have been looking around and considering the:

XFX GeForce GTX 260 Black Edition 896MB GDDR3 PCI-Express for £150
which supposedly has comparable performance to a 280

and then I'm at a loss for new CPU. Given that Core2duo's still seem to be as good as quads for gaming, and im not looking to update the whole motherboard to go i7 what would you suggest?

Main aim is to have a system thats going to handle Modernwarfare 2 on a 22" monitor at good/high graphics detail with no fps loss.

cheers in advance for any opinions!

thanks for the reply, do you reckon that new CPU would offer better increases ie. if i got it to 4ghz to make it worthwhile or would you put all the money into the GPU?