I would tend to think that at lower volumes, the fan might not actually come on(unless it's constant) and at higher volumes, which is where you'd probably be using it(otherwise why get the amp) you'd drown out the fan noise. There's also quieter fan mods out there to, if in fact, it's an issue(swapping to quieter fan, or attenuating existing one).

Half of communication is listening. You can't listen with your mouth.