Other mod to make more quieter PSU is get a low current 12V 3 wire fans with one exception not any fans: Get one from Nidec, San ace/Sanyo, YS Tech, NMB, PAPST. Anything less than 90mA will be quiet. If hair more current, I would try that on wired to 5V instead. This way you get high quality fan and will spin quietly. That providing that heatsink is oversized and of good quality.
Coming from me being deaf using hearing aids bit odd but make sense as I have hard time hearing other sound if the noise is white noise and too loud that fans generates. Back in the day when I had Athlon XP machine, I had to resort to a home made adjustable voltage regulator and 5V mods to run fans, that I have at hand or was with PC, more quietly and that was before I used ebay more.
Don't forget, the type of motor that has very soft magnetic cogging that is very soft vibration when hand-spun tend to be smoothest and transmit less vibration into PC too. The one that cog harshly will buzz loudly like a tired bug trying to buzz off into air when spinning slow at reduced voltage/power, hold one and pick one that is smooth running.
These days, I'm glad for PWM technology.
Great Northern aka Canada.