After 8 months of living with the TKPower 300, I have just one word for this PSU: Wonderful. (See the article on TKPower + VIA C3
on the main site: http://www.silentpcreview.com/goto.php?t=s&id=18&a=1
Using a PIII Tualatin-S 1.1 cpu and 3 very low-speed Panaflo 80mm fans (FanMate'd) inside the case, cpu temps are always 49-52, hard drive temps 36-39. The system never crashes, and does everything I ask it to do very quickly. It is dead quiet.
This system is only drawing about 67W, total. Even at that level, the top of the case directly above the PSU is fairly hot to touch.
I suspect that the TKP 300 could run with much higher wattage systems, but better heat dissipation would be essential. As a first step, a low flow fan inside the case blowing across the PSU could be tried.
If you can get along with a processor which does not generate a great deal of heat, and if you don't mind a bit of installation hassle, the TKP 300 is a great choice.