I find Radions to be loud only if allowed to get dirty. If cleaned regularly (at least for me) I really can't say they are loud at all. And I have over a dozen running on many different setups.
For the most part cleaning is mearly running a shop vac over the fan every other week, then take apart and clean once a year. No complaints using this method and with these units.
But my customers already know not to expect silent if they want a well designed system that truly recreates a piece of the Ocean.