I also do not know much about AMD overclocking either, but ...
Your power supply is not your problem. Under full load, your system will not pull more than about 450 watts and you have a better than average PSU.
IF you run Prime95 to stress test your overclock, what are the results in the Prime95 small fft's test and the blend test? Small fft's primarily tests the CPU. the blend and large fft's tests work the memory harder. This is how you can get an indication of what may be wrong.
Next, I think you may not be monitoring your core temps properly. Generally, idle temps run about 5 - 10 C above ambient air temps (usually room temperature).
How are you monitoring the temps? And with what?