I have a bonus room over my garage upstairs, which is at the end of
about a 40' run of 12x8 duct (furnace is downstairs on opposite end of
house). My heating is zoned (up and down), but the only way I could
get any real airflow to the bonus room was to close down way too far on
the branch duct dampers upstairs.

I installed a fantech FX8 8" inline fan as a booster fan, controlled by
a thermostat in the bonus room (using an Argo AR822 relay). I used
sound isolation mounts (rubber plate form mounts from Mcmaster Carr),
and the fantech neoprene mounting clamps to connect it to the fuct work
(prevents transmission of sound).

It works great, and I cannot hear the noise of the fan when standing in
the room directly below it. It provides alot of air, and has solved my
heating problems.

I read some previous posts on this board talking about too much noise
or ineffective fans. This solution works great.