They are cheap enough. But I don't recall them being very quiet. You ight check the website for WM and see if they have Whisper filters and how comparable they are to the other stores. They will ship to your closest store for free if I remember correctly.
The nice thing about those is that they have rubbery type feet and aren't apt to rattle into things. I have had to lay one of my older type square air pumps in a wash cloth behind the tank sideways to keep it quiet and let it breath. There are little air filter pads in some models which are replaceable to help prolong life and stay quiet.