Antec is a recommend AMD power supply. I have two Antec towers with Antec PP303XP 300 watt power supplies
One computer is a Soyo SY-K7V DRAGON Plus! with an Athlon XP 1800+ CPU, four 80 GB 7200 RPM hard drives (on the RAID connectors), and four ATAPI devices.
The other is an ABIT KT7A-RAID also with an Athlon XP 1800+ processor, four 7200 RPM hard drives and four ATAPI devices.
In addition, there is networking, modems, USB devices, sound cards, etc.
I have had no power supply problems with either computer, although I am probably pushing my luck with all of the stuff connected.
Just as a longshot, you may want to do a visual inspection of your motherboard (checking that connectors are seated properly while you're at it) for evidence of Leaking Capacitors Muck up Motherboards
. ABIT among others is known to be affected by this problem.
You might also check out (if you haven't already) Paul's Unofficial ABIT KT7A-RAID FAQ
, the very best ABIT FAQ site. There is a wealth of troubleshooting tips and general information. Paul Howland has a PhD and Masters degrees in Electronic and Electrical Engineering and is a Principal Scientist for NATO, doing research on future radar systems. He did the FAQ's in his spare time.
By the way, under instabilities he recommends a minimum 350 watt power supply. This is probably good general advice, but not all power supplies are created equal and my experience with the 300 watt Antecs continues to be satisfactory.