2028 is pretty quiet. In a closed cabinet under the aquarium I could never hear mine. Wish I could say something about the pro3 but unfortunately I haven't tried that one yet.
Only have had my 2075 running for two weeks. It is running in an open stand sitting on the floor. I have to put my hand on it to make sure that it is running, very quiet. Only sound I ever heard is when it was touching the stand, low vibration. If I was putting inside a stand I would sit it on styrofoam to isolate the vibration.