I have a Enlight 300W running a Celeron 1.43GHz, (4) 7200RPM HDs, (3) CD Drives, (2) Video Cards, TV Tuner, NIC, Sound Card, IDE Contoller, 3 case fans. I had the same configuration running on a generic 250W previously. I've been using it like this with no problems for about a year. The voltage readings look fine.
I used that power supply calculator that was posted somewhere here before. It strongly recommended I have 450W
I'm getting an Antec TruePower 430W on Monday though, in anticipation of adding even more stuff