I actually hear a loud whirring noise coming from the wet ends, not necessarily the motor side. Our motors are in the fish room, separated from the house. the "noisy" side for us is the viewing pane, although I realize that a noisy motor could be vibrating through the tank. But with our tank being 1/2" glass and that we still have the pin spacers installed and in use, I am leaning away from that as the cause of the noise.
I do agree that it is hit and miss. Of our 4 pumps at least one is quite quiet.. another is relatively quiet and the other 2 are noticeably noisier.
We did have a noisy motor, but ETM swapped it out for us under warranty without any hassle. But the "noise" on a wet end isn't really a warranty issue, beyond a bad bearing, shaft, etc. And all of ours have already been replaced in December (not to mention our wet end warranties ran out last week).