I'm using 2 X Eheim 1262's + 1 FX-5 on a 300 With 90+ gallon sump... super quiet. The Eheims are slightly louder than the FX-5...and I can't hear the FX-5 unless I'm right next to it and nothing else is on in the room. Very faint humming from the Eheims. If I wasn't such a procrastinator, I would finnish the doors for my stand and install them. I'm sure you wouldn't even know the tank was running if the doors were on. I'm presently running a Rio 1700 on a 55... it's dead silent. A friend of mine runs 2 X rio 17 HF's on his 180...louder than the Ehiems but not much. He did say that he had to tinker with them a bit to get them that quiet...not sure as to what he did though.