How much could i overclock my Q6600 with this cpu cooler?

My guess around 3.2ghz worst case. Other factors come into play though from the case to your ram and mother board, even your power supply.
 
For that money, y not get the Xigmatek??? Its cheaper and the best air cooler behind the TRUE (but the TRUE needs lapping, and some good fans to win)

Edit: oooo i didnt think u already had it....in that case it should be fine
 
dasher I've have had the coolmaster hyper tx2 for 2 1/2 years and it has been a good cooler.the newer one should do good in oc cpu.