I've got an AMD 6300 and the same motherboard as you, Corsair 600W bronze PSU too so our setups are similar enough and I'm having a nightmare of a time getting it to go above 4.2-3GHz.
The voltage requirements keep going up and up and cores keep failing, I've tried FSB overclocking and just upping the multiplier, it's not a good GUI for overclocking in the bios.
I've actually been trying again today and it's just not good at all, I've had BSODS and core fails every time I try prime95 on speeds above 4.3. Temp isn't an issue, never gets over 60C as I've got a good cooler.
I'm going to revert to 4.3GHz on the settings that seemed to work and then give it a good run on the stress test and see if it's actually stable, will let you know what settings I used when I know its safe