I'm running a bog-standard 300w case PSU driving 1x HD, 3x Optical, loaded out with PCI cards (4, SB Live, Ethernet, Modem & SCSI).
512Mb SDRAM, Athlon 1200TB, Geforce MX440
If it was a more powerful graphics, I bet it would tip the balance.
Got a 3rd upgrade PSU to go in, after QTEC 450w dual fan (returned due to inaccurate -V), No-name 400W dual fan (died).
To go in, Winpower 450w, 120mm fan - so far, the 120mm fan PSU's seem to have a little more class than the single and dual 80mm.
On the other hand, I have the greatest respect for "Maxpower", the brand of the case PSU, as this unit also survived a cookout when the fan failed - it took a lickin' and kept on tickin' - so if I saw Maxpower as a replacement, I'd rate it considerably better than most of the bog-standard ones.
The no-names and off-brands are hard to judge, though a cheap 300w is more likely to make it's rating than a cheap 500w - probably the same 300w unit with only minimal component uprating.