okay, i know this is an older thread but cant pass up the oppertunity.
anyrate with an asus board you dont need to bother with anything if you want to overclock casually, so VT-x and all that can stay.
also leave the voltage on auto and crank the multiplier up to 42 or so and boot if she boots fine the stress and check temps, if all is well then keep pushing else just take the voltage off auto and set it to a + value and just make some more like make it 0.2v over stock or something.
as far as safe voltage goes, anything that doesnt push too much heat is fine and btw people get scared at 80 deg but thats fine so just keep pushing till temps make u go off or volts or it becomes unstable