Thanks for the info. I think that the way I am going to go, but need to make sure I can get it silent. My son room right next to area the QT will be in, and years ago when I had it setup, we could hear it in his room. Whisper pump, was anything but whisper. haI keep everything in a maintenance "closet", a 6'x6' room with a door, so I don't worry much about noise.
that being said, these aren't that noisy when i'm in the room. I have a larger sponge filter that I need to modify because it doesn't have that turn over like these and it just bubbles too much.
to keep noise down I keep the water level just over the bottom lip of the 90 so air can escape w/o bubbling too much.