We took two approaches to overclocking on the M4E. The first was through ASUS's Auto Tuning feature from within TurboEVO application. Furthermore, there are two options to choose from: Performance and Extreme. The Performance option only deals with the overclocking of the CPU, while Extreme deals with the overclocking of the CPU and RAM together. We took the Performance route and netted a 4.2GHz. A decent overclock in our books, but could be better.
The next route we took was manual overclocking the board via the BIOS. The only options we played with was the rising of the CPU voltage to 1.4 volts and the CPU multiplier, which we maxed out at 48x under this voltage setting. The system was completely stable as a 24/7 gaming rig.