Seasonic S12-600 PSU

The Seasonic S12 series power supplies are simplistically elegant. There is nothing on the power supply that does not add functionality. No flashing LEDs, no unnecessary switches, nor glow when powered on. It has just one big 120 mm fan. Depending on temperatures, the fans adjust to minimize noise or maximize fan longevity. Larger fans have the advantage , they can spin slower and therefore quieter , while still pushing the same volume of air , as a smaller fan. I currently lack a decibel meter, but by doing my unscientific "how close do I have to get to hear it test" , I literally had to get my ear within 2 inches of the power supply to the the system. Unless you go fanless, you'll be hard pressed to find a quieter power supply.