However if your PSU is some terrible brand or low quality, you might have some troubles with it, also overclocking the GPU will most often give you little FPS boost and lot's of extra heat, which will most likely reduce the life span of the gpu, so my advice is if you don't really need the extra 5-10 fps you will get (if you get that much), just don't touch the GPU. If you decide against that, go at slow steps, increase little by little and do extensive stability tests after each memory+clock oc.