Don't bother trying to find a 30 sh PSU. Never buy a cheap and nasty power supply they can go wrong and take out all you other expensive components at the same time. Not only that just because it is marked 500w or 600W often they are nowhere near that rating. Purchase a good make like Seasonic, CWT, Corsair, Thermaltake, Enermax, Gigabyte, Coolermaster, Antec, etc and try and get one with a single 12V rail if possible. I would advise you to get one of about 650W minimum depending on your hardware demands.