I have a Q6600 G0 stepping 2.4ghz overclocked to 3.0ghz (375 x 8). However, my temps seem to be much too high, idling around 42~ and maxing out during games at around 64~.
This is AFTER I have lowered my clock from 3.2ghz (355.5 x 9). My initial temps were hovering around 39~ idle, until one day my computer said it couldn't post the clock.
I keep all of my core voltages on auto, and I have never had any problems posting a clock.
The VID on my Q6600 is 1.200V, which to my understanding is extremely low for a Q6600 and that I am apparently lucky.
For my cooling I use a Zalman CNPS9700, which I understand isn't a premier cooling unit, but I have seen posts from people using the same cooler and hitting the 3.6ghz mark while remaining very cool (ie. 32~ idle).
I use artic silver thermal compound and followed precisely the directions (horizontal line with "greying" on the heatsink itself).
I would suggest never overclocking a CPU and using auto-voltage. I did once on my 720BE and instead of the required 1.465V it would randomly drop to 1.1 causing the computer to freeze up pretty often and even crash.
Temps don't seem so high, depends what cooling you have?