I have these parts and I was able to get 4.0 ghz stable and at The CPU vid is 1.4000 and the NB vid is 1.2250 in AMD overdrive and I am running pretty cold (below 50 c) also I ran a stability test in AMD overdrive at 4.2 ghz and I didnt crash but I got: calculation test hardware failure detected. Here are my parts and can I get any better than 4 ghz:
http://pcpartpicker.com/p/6F2hhM
http://pcpartpicker.com/p/6F2hhM