Panasonic whisper green is a really nice one. As far as venting out the soffit that is just a vent cap and the unit has a built in backdraft damper. Several different models with different CFM ratings based on how much ventilation is needed and they even have a calculator that sizes the fan for the room to be ventilated. http://www.panasonic.com/consumer_electronics/ventilation_central/chooseyourfan.asp
Here is a model that has a built in occupancy sensor to simplify operation and meets the needs of most bathrroms, 80 CFM
http://www2.panasonic.com/consumer-electronics/shop/Building-Products/Ventilation-Systems/Ceiling-Insert-Fans/model.FV-08VKM1
Tom Pittsley
[email protected]www.eebt.org