I think a good potentiometer would be fine. We are not talking huge amounts of current, plus it give you an easier way to manually control speed. For the matter of current, you may even look into a varistor if a pot wouldn't be robust enough. I seriously doubt you are running big steel bladed fans that need amps of current.
If you wanted to get really crazy, you could mount a temperature switch to the coolong coils in series with the fan power and have the fans kick off and on at your own predetermined temperature window.
As for fan noise, I would look into mechanically isolating the fans from their mounting with a neoprene or foam rubber gasket. This would virtually eliminate mechanical vibration noise. If it is motor humm you are hearing, then the fans are loading and you may have cheapo crap motors.
Reduce air flow may result in temperature increasing and your pc may turn off. Better way i can suggest is pwm driver dependind on the temperature but also change your fan with a new one low-noise and good quality.
Reduce air flow may result in temperature increasing and your pc may turn off. Better way i can suggest is pwm driver dependind on the temperature but also change your fan with a new one low-noise and good quality.
