If you're completely stable there, and the board is not heating up...I would leave it be. 1.55 vcore is the absolute max AMD engineered for the chip. You have a good OC though if it's stable and you're not experiencing any board issues. You may be ok there since you're using a 4300 on that board. If we were talking about an 8350, I would doubt you could sustain such an overclock on that board without heating up the VRMs quite bit more than they should be.