Hi ManuelJ and welcome to OC3D :wavey: FragTek is right, it totally depends upon whether your PSU is a no name generic one or a recognised quality brand; and it also depends on whether the voltages it's supplying your system are stable/solid enough. Some of the preferred brand of PSU recommended around here for OCing are Tagan, Enermax, OCZ and PCP&C, because they provide ample stable voltages for OCing on whatever platform you're using. Quite often you'll find generic PSU's don't get even close to the voltages that they state on the side of the case.
Secondly, it totally depends on what your system consists of and what extra 'bits' you have included, as to whether 430W is gonna be suitable. Again, like Frag said if you're wanting to run SLI, a watercooling setup and a whole heap of case bling and fans...then no, you need to upgrade. What brand PSU is it anyway mate?