Well you can get a nice looking antec case with a 400+W antec psu for less than for instance an antec truepower 430W by itself. I dont think theres really any need for more than 400W, and antec PSUs can normally take a pretty good load (more generic ones tend not to live up to their spec'd power).
Omardeth I know is big on the "Achieve 500W" psu thats dirt cheap.. so he might recommend tthat too you. Definately a good possibility for a low cost option.
Link here...
http://store.yahoo.com/akidacomputer/acpowsup50du.html
Personally I run an Antec TruPower 430W, but it was probably overkill for my XP 2000+... my generic 350W PSU died so I decided to get something that I hope will last awhile