That's a pretty fine overclock. I've also been playing around with my cpu today and managed to push it (not very sucessfully) to 4.5, I tried 4.6 but it wasnt working that great and because I'm not exactly comfortable going over 1.39v on the cpu vcore. 4.5 was stable for a couple of hours then the bsod's started so I just went back to 4.4 as a failsafe.