Ive been running a AquaC Pro /w a quiteone 3000 hanging off the side of a 20gal sump inside a cabinet, i find it to be far louder than i had expected. I think the spray injector is causing all the sound, though the only other systems ive seen are at my local fish store where hes got a corallife super skimmer going on one of the tanks and it is many times quieter than my aquaC.
If you go with a remora i would defiantly recommend wrapping the collection cup in wet paper towel which will make a good seal around the top of the skimmer which does cut down on the noise a little.
-Aaron