It's not really the wattage but the amperage to look for esp. on the 12 volt line. You need to look at the power requirements of each component and make sure the supply you use can meet them. My PC has 9 drives (IDE & SCSI drives Mac and Amiga emulation) etc. and my 450W copes with ease.
I went to a local PC builder shop and brought what they use in their OEM machines, inexpensive ($69NZ) 1 year warranty, a good supply. If you want I can open the case and report the Amp specs and manufacturer.
