Quality of the PS is perhaps even more important that the rated watts--I'll take a 300 watt Sparkle, Enermax or PC Power & Cooling any day of the week over some no-name 400W unit. Wattage is really kind of overated--clean, consistent juice is more important that the nominal wattage. You're not buying a hair dryer, after all. A quality 300W unit will power your system with no problem.