I've got an AS GAM5 system with an open return. As many of you have told me, one of the reasons why it's so noisy is because it's an open return and because the GAM5 is a positive pressure system with the blower on the bottom.
So what I'm wondering now is this: how much of a pain in the rear would it be to have a contractor turn my open return into a ducted return and put some grilles throughout the house.
Here's a video (you can ignore the commentary) of what my system looks/sounds like in operation:
As you can see, there are ducts already going to the lower floors so I'm thinking it might not be a huge deal to put some returns downstairs, though I'd ideally love to have a return in every bedroom upstairs with the whole "hot air rises" thing.