About the power hungry boxes... I experienced that a 300w rated psu from a mid market brand (aopen) wasn't enough to power up an AMD64 2800+, with 1 SATA hdd, 1 DVD rom, 1 120mm fan and 512M DDR, VGA and sound onboard... the problem was not enough power on the 12v rail. An Antec 350w psu had no problem att all powering such a box. Important is the combined power output on the different voltage lines without affecting the voltage rating.

So new power hungry components like the latest AMD64 and intel p4 cpu's, 7200rpm hdd's, and specially the new vga-cards like the ATI X800 or Nvidia 6800 need a decent power supply that can power your box with clean an stable power without getting to hot.

I would go with a not to high rated but decent power supply. Brand's I suggest, or trust when buiding a box:
- Tagan
http://www.tagan.com/main.htm
- Antec
http://www.antec.com
- Enermax

Keep in mind that today psu manufacturers make models with several fans, suggesting the more fans is better... this is not entirly the case. For the simple reason that those fans take up place where other (better psu models) have larger heatsinks or larger capacitors, you can also notice the difference in weight. So a so called fantastic psu cause it's not costly and has a triple fan design is probably a bad choice, better go for a design with less fans (1 or 2) but better components inside. Heatsinks generate no noise, are not moving and therefor much more reliable, and don't consume energy. When you take in mind that some manufacturers can build psu's without fan's, a pure fanless design (Silentmaxx Pro Silence, Yesico, Antec Phantom) you wonder why others need three fans? inferior design and show nothing more.