Great, now I've narrowed it down to the blue aluminum heatsink on amazon everyone seems to be using (copper would maybe be too heavy without a support arm), or the hyper 212 as an all-in-one solution...not sure if that would work though:
https://www.amazon.com/Cooler-Master-Hyper-Direct-Contact/dp/B005O65JXI
The stock cooler generally does fine, but the best cpu fan on the market IMO is the cooler master hyper 212 evo, which you can get for $20-30.
https://www.amazon.com/Cooler-Master-Hyper-212-RR-212E-20PK-R2/dp/B005O65JXI
Throw a decent cooler on that Q6600 and overclock it to 3.0 GHz. Then replace that 9500GT with any of these graphics cards bought used on eBay and you'll have a pretty competent gaming rig that can handle most games released through 2013. Total cost will be around 80€.