To be clear, PSU stands for Power Supply Unit. This is the one that feeds power to the motherboard, drives, fans, and sometimes vidcard. Generic supplies are notorious for going bad in very subtle stages or catastrophically sometimes (pumuputok). Yung luma kong PSU, di ko napansin na unti-unting bumababa ang current ng 12V rail nya although voltage was within 10% tolerance. Since then, nag branded na lang ako pero with matching research sa internet kung oks naman performance.
Yung mga external power supplies naman, kung hindi AVR, UPS (Uninterruptible Power Supply). May bad experience din ako sa mga AVR. I recently discovered na yung AVR ko was putting out too high voltage naman! Around 260VAC!
Kung di ko na-measure ng multitester yan, I'm sure puputok eventually ang power supply ko. Nag straight UPS na lang ako since then; for 110V, naka transformer na lang ako. If you want medyo sure na AVR, look for the moving coil designs (yung mga naunang AVR na mabigat).