I would expect the CX430 (or any decent quality PSU 300w or more) to be sufficient for your setup, your GPU probably uses < 75W and the CPU probably < 125W. You really don't need a higher power PSU, as long as you don't buy a junky one.
If you upgrade the GPU, the CX430W will probably be good for this gen GPUs < 200$. If you want to go a little more powerful, 60$ can get you this http://www.newegg.com/Product/Product.aspx?Item=N82E16817151093
That 520W would be all the PSU you need for a single GPU system in most circumstances (it maybe a little low for your super high end GPUs, but I'm guessing your not about to drop 400$+ into a gpu, or for obsolete high end cards).