Neoseeker has published a review of the Core 2 Duo E6600

Just like with our E6400, we were able to reach almost 3.2GHz with just the Intel supplied heatsink - however we knew that was not the limit of this processor, so we switched coolers and used a Noctua NH-12 to try to find the real limit of the processor.

Using our Asus P5B, with the latest BIOS, the Noctua NH-12, and two 63CFM 12cm fans, we were able to reach a whopping 3.48GHz with just air cooling!

I am not talking about just posting, or getting to the Windows desktop - for those metrics, we were able to reach up to 3.7GHz - I am talking running our whole set of benchmarks, without problems, and being completely stable at 3.48GHz.

Intel E6600 Core 2 Duo Review