OCZ Powerstream or Modstream, 520w I have was $99 at
www.monarchcomputer.com
Note: If you have a midtower case though, be warned that the Modstream has shielded power cables that are hard to bend as you need them to. Dunno if the powerstream is the same way, but these powersupplies have great cooling, are quiet, supply clean filtered power and have been highly regarded by many. They are also PCI-e compliant