What resolution do you game at?
It's almost certainly not worth upgrading for games if you're gaming at 1920x1200 for example.
If you just want a new CPU to play with, that's different, but if you're upgrading to improve your FPS, I think you'll be disappointed.
Take a look at games performance in Dirt2 @ 1600x1200 for example:
http://www.techreport.com/articles.x/18581/7
i7-980X = 74 FPS and £800
Core2 E8600 = 62 FPS and £129 (this is roughly equivalent to your overclocked chip)
In Left4Dead @ 1600x1200:
http://www.techreport.com/articles.x/18581/9
i7-980X = 97 FPS
Core2 E8600 = 97 FPS
As you can see from my sig, I'm huge believer in spending twice the cost of the CPU on the GPU.
In short - my recommendation is to get a new GPU if you want better performance in games.