A 500W PSU would be sufficient for that build, provided it is a quality brand like Seasonic (or one they build). I would not use a (non-modular) Corsair CX though, as they were built by CWT using some inferior Samxon capacitors that don't like heat and are known to fail early. The modular ones used quality Japanese capacitors and are fine. Any of them would be good in light duty office-type PCs, but I would not use a non-modular one (with the dicey capacitors) in a gamer.
Some good alternatives include the Antec Earthwatts (built by Delta) and Rosewill Capstone (built by Super Flower).