I have been looking at add-on furnaces for a few months now and the PF100 seems like a good choice. I have 3000sqft to heat on two levels. Each level has it's own zone and currently connects to a propane furnace. Anyone have any opinions or comments regarding the PF100? I looked at other models, such as the Fahrenheit Endurance and St Croix Revolution, but fear that they may have some difficulties heating the house. Also, the Harman dealer is just a few miles away.