Got my system running again after about 7-8 months of not working. Thought I'd fried the motherboard, turns out the cpu power connector on my PSU stopped working. Funny I didn't test it sooner.
This time I'm spending a few days finding the right settings to run stable, since I ran into some stability issues before the PSU went stupid.
What's looking like good results so far by testing with Prime95
400MHz FSB stable with FSB voltage +0.2
Q6600 3.6GHz stable with motherboard set to 1.54375v which equals 1.47v idle, and as low 1.41v under load, any lower setting and it bottoms out at 1.39v and the system reboots.
All I have left is to figure out what I want to do with the memory, I can run it 800MHz for 1:1 ratio, and tighten down the timings, run it at 1000MHz which is as close to the stock speed (it's DDR2-1066) I can get it, or try overclocking it to 1200MHz.
EDIT: Switched to IntelBurnTest, the computer just shuts off after a few minutes when overvolting the cpu, temps are only hitting 54-55c tops, thinking maybe my PSU is b0rked. Never going to buy a cheap one again though after the power connector failure, same goes for the case. Suppose i'll try again in a bit disconnecting every drive/fan I don't need.