I've been telling you that power supplies from years past are often not good enough for today's motherboards and chipsets. I've been talking to techs and white box builders about it and they agree in the main with my observations.
PC power supplies have adhered to a standard deviation in voltage on every circuit of plus or minus 5%. That was perfectly adequate for the parts we had then. Some of the higher priced, brand name units performed in the neighborhood of plus or minus 3.5%. Now, it seems that the most modern processors and chipsets require a little better. Plus or minus 3% is the figure I heard the most, with a few saying 2.5% was needed.
A machine will run without damage with the looser specification power supplies. Some few will be unstable, though, and the techs I spoke to make a point of swapping the power supply early in the diagnostic process.
The good news is that making these more tightly spec'd power supplies is within the reach of every manufacturer and some of them are already doing it. The cost added by this is minimal. You will end up paying more for the increased capacity today's systems require than you will for the tighter output specs. A lot more.
Until the manufacturers wise up and start posting the tighter specs, stick with the really well known name brands, such as Antec and Solar. There are others, but I just can't think of them off-hand.