Any further bump in voltage will increase your temps at load, I would reccomend a cheap after market cooler, such as a the 212 evo.
@esrever, overclocking isn't just about the FPS boost, it's about the bragging rights!
People have gotten as high as 1.5v core, but I wouldn't reccomend it. I presume you've disabled stepping and CNQ?
According to AMD, max is 1.55V, but it depends on your temps as well. Have you fed your NB a few extra V's?