Help finding a CPU upgrade

[Ragequit]

Hey guys and gals, I'm relatively inexperienced with PC components and I was hoping that someone can take a look at my build (below) and recommend a good CPU upgrade that won't require a new mobo. Is it worth getting a Quad-Core with my system? Thanks in advance people!

Rampage Formula mobo (uses socket 775)
Intel duel core 6600 @ 2.40GHz
3.25 GB of RAM
Nvidia GeForce GTX 260

 

[Ragequit]

im willing to spend around £200 for one but ive been told the i5 wont fit my mobo socket?

 

[Ragequit]

well im upgrading for Skyrim really, my system keeps up pretty well with newish games so far but i just have money to spend right now and I want a new CPU.

someone told me that the best CPU upgrade i can get right now is this http://www.overclockers.co.uk/showproduct.php?prodid=CP-281-IN&groupid=701&catid=6&subcat=567

but do you think I will notice much of a difference?