Personally I have a Rhéobus on my box, which allows me to control its speed and brightness (proportional to velocity). A 5 Volts is inaudible but not blow the masses, to 9volts it starts a little to be heard (AC buzzes a bit) but it blows more. But at 12 V, it is as a desktop fan!
So depending on what you are looking for power or silence, to make a choice!
However, I have bought 2 for my turn, because personally noise does not bother me, having been accustomed to pc much louder than that.