Listen to GeneO.
I used the automatic overclock on my ASUS P8Z68-V Pro and it got me to about 4300MHz on my (stock 3400MHz) 2600K. It also ran my CPU voltage up to 1.58.
When I set everything manually I was able to hit ~4700MHz (stable) with the voltage at 1.37. You can imagine the corresponding lowering in my temperatures at the lower voltage, too.
Also, I never had any luck at all with the ASUS AI Suite. It took a lot of massaging to get it to install and it didn't get me very far at all. I'll admit that I didn't mess with it long enough to really try it out, but for me it just wasn't worth it. Others may have better luck than I did, though.