The Antec SL300 PSU included with this case sells for about
$45 shipped by itself. It has a 3-year warranty and Antec has a pretty good reputation for getting stuff handled if you have a problem (I had to RMA my Datachute PCI to them, got a NIB unit in return).
The SL300 has 220 watts available on the 3.3V + 5V combined lines. This is really good, more than most generic-brand 400W-450W units... an honest 300W unit and then some. I would use it on mid-line AthlonXP systems, but if you're planning to max your rig out with two hard drives, two optical drives, two or three DIMMs, an XP2200+ or higher, and a power-hogging Radeon 9700 Pro, then get yourself a TruePower 430 or an SL400 for some reserve power