It depends on the fans top speed.
When my system starts, the fastest fan can not get past 1200-1300 rpm so is considered more quiet then having a 2000rpm fan run full speed.
If you can live with one speed or manual speed control, you can use a fan controller(or 5 volt mod some fans
) to set the speed once and it will always run that way.
This is not always recommended for cpu fans as with the board in control at least if it gets too hot, it will crank the fans up, while if you set it too low it can overheat with the board not being able to auto control the speed.
That being said, some heatsinks are more then capable of low speed cooling.