Upgrading my bottleneck computer

[grimreaperpt]

Hey guys,
I recently bought a nice graphics card, the ASUS HD 6970 2GB. It's supposed to be really nice but i think the rest of the components are a bit outdated, because i don't feel a big difference in videogames (sorry for my bad english btw...)
morrowind and oblivion are still having fps problems, the witcher 2 it's really slow (around 20fps), but crysis 2 is running ok with high specs... I don't get it...

Anyways, my specs are:
motherboard: gigabyte ga-p35-ds3
CPU: Intel 2 Quad Q6600
memory: 4gb DDR 2

so... do you guys think i should upgrade? i don't want to spend more than 300€ (maybe 350€ if it's really worth it)
should i go for an intel i3 or i5? and what motherboard should i go for?

 

[Cygnus x-1]

It might be time for a fresh install of windows, and a little overclocking on the q6600. That said even at stock, you shouldn't have a problems with oblivion.

 

[Uther39]

Keep what you have, re-instal windows, buy a coolermaster hyper 212, and OC your Q6600 to at least 3Ghz.

 

[grimreaperpt]

I think my graphics card is ready for overclocking, it looks like this one:
http://www.tecnologiasdeultimogrito.com/wp-content/uploads/2011/01/asus-radeon-6970-directcu-01.jpg

I never overclocked before. Is there a recommended software to do so, or some special care I should know? (for example, maximum recommended temperature)