Antec, Enermax, or Sparkle Power 300+ Watt would be mine.
AMD has a list of good power supplies on their list. You can tell a good powersupply from a cheap one when you see them. Look for heatsinked components, a ball-bearing cooling fan, and plenty of connectors.
Power supplies included with the cases you will buy in most computer stores are not going to be top of the line.
