hi, well I just kind of answered the part of the question myself, I have just overclocked to 4.02GHz, and my PC booted up just fine, Temps are around 25°c sometimes lower but never hardly much higher. I think that is as far as I should go, I'm happy with that, of course 4.2 would be better, lol. This Thermaltake Frio sure is a good CPU cooler, the fans that came with it go upto 2400rpm, I took the speed controllers off a while ago and just twisted the 2 ends together on each of the Fans and heatshrinked over them, I then have 1 Fan on the CPU Fan header and the other on a Zalman Fanmate, the Fanmates work good, giving a good speed range and decibel range too!, yes the Frio can be loud on full blast but at half speed you can't hear it, hence the use of the Fanmate, the speed controllers that came on my Frio both fell off to be honest due to brittle wiring where the potentiometers(speed controllers) had been soldered on, the wire is so thin it just snaps apart, it can't hold the weight of the speed controller knobs(potentiometers), and it's really difficult to solder them back on. The Frio does have its faults but if you like modding things then its not a problem, the mounting brackets aren't so good either, but can be fixed up with some washers and better nuts. Just checked my Temps and the CPU is at 23°c now, it' actually the same as when my CPU was as 3.4GHz, the Temps are the same, the overclock hasn't really changed the Temps at all, down to the good CPU Cooler I would say. I just wish I could unlock my CPU, I think it could be down to either both my CPU's not being unlockers or this Motherboard I'm using, no offence here to Gigabyte but I have feeling it is this motherboard, apart from unlocking Cores this is great Motherboard so far.