Hi, a decent 500W PSU would be sufficient for most PC's not running a high end graphics card. Some of these bad boys can draw more than your CPU! Try to stick to well known brands like Antec, Coolermaster, Corsair, Enermax, Hiper, OCZ, Tagan or Zalman. If I have forgot some other people will mention them.
Seasonic is also a very good brand, but any of the ones phill2000 mentioned are top quality. Do ever cheap out on your power supply, it can cause alot of tears later on. Peace
they are alright. good for the mid end, btu nto top noch. the best 5 have to be (in no perticular order) PC Power & Cooling Corsair Seasonic Tagan Enermax