I found the most stable overclocking for my Anthlon 860k was at 4.3ghz. If you look at all the different tiers of the Anthlon cpu's, you see the fastest cpu runs turbo up to 4.3ghz. When they make the cpu's, they design them all to run at 4.3ghz, but due to the heat output they underclock them to run within the thermal range. I put a Cooler Master Hyper 212 evo aftermarket cooler to overclock mine and found it ran easily at 4.3ghz without the need of tinkering with the voltages. I also have the same Asus A88x plus motherboard as you, which made it very easy to go into the bios and change the overclock speed, so you don't have to change it everytime you boot up with a crappy program. I'm sure with a lot of tinkering with the voltages you can overclock it higher, but with myself also being relatively new to overclocking, I found it easy to just set it and forget it. Hope I helped provide some insight, and let me know if you have more questions!