You'll be fine with basically any PSU with 350w or more. Hell,
www.directron.com has had some 400w RAIDMAX PSU's on sale for $8 before. If you have 1 HDD and regular PC components then you don't need anything special.
Of course, if you want a damn nice PSU, I suggest Sparkle, Enermax, or Vantec (Sixate says they're good). I've heard good things about those three. You'll definitely get the best performance out of a quality PSU, but for normal usage, a cheapy RAIDMAX or POWMAX PSU will do fine.
-Lasereth