Me and my room mate have purchased an E6600 and overclocked it to ~3Ghz. Now we have pretty descent hardware (DDR2 800 RAM, a Tuniq Tower T-120, and it's in a cool Antec P180). We stopped are clock at ~3Ghz, because we were afraid that if we went any further, we would end with a burnt CPU. I'm not sure of it's current temperature, but is it possible to overclock this baby to ~3.6Ghz, or is there a limit where our Tuniq Tower will become useless. Also, I was wondering where we should stop the CPU voltage.
you shouldn't have to increase the voltage too much, you may get problems overclocking with it too high, just watch the temperatures, and increase in small incriments, cheking for stability with memtest as much as you can. It will take a while but it can get you higher. Also, if your that worried, some motherboards give you a shutdown temperature, where if it gets too high, it will shut down your pc automatically, but I dont recommend using it becuase the onboard sensor is usually wrong. Just raise your voltage a small amount, and increase clock speed. when you hit a wall, increase the voltage a little more, but make sure to check the temps afterward.
EDIT: The CPU temp should be in PC health in the bios, Im not sure on exact numbers for your VCORE, Im running a 478 prescott, which have completely different values.