Following up on the installation of my room to room heat transfer, almost two years ago when installed. Results are good, and house stays warm throughout the night on cold nights, 10-30deg F. One change I recommend is using a larger duct fan, maybe 8in with more than a .3 amp motor. The only fan available at Home Depot was the 6in duct fan .3 amp motor and 25ft of insulated 6in flexible ducting, which is another change I would make, to install with solid ducting for a smooth transfer of the heat.
However, I am pleased with the results of transferring the heat to the other part of the house and it give it just enough keep the house comfortable.
I do like the ideas posted for using a solar panel from the fire light, not sure how it will hold up to the heat. Reversing the air flow of pulling cold air to the fire source through the ducting is also a great thought, maybe ducting under the house instead of through the attic space since cold air is lower than hot air.
The inline ducting produces no noise, only the slight rush of the air coming out of the register I installed in the hallway just before the living room. I also use a ceiling fan in the living room, which helps with an even distribution.
Thank you for all the comments and ideas, I really like this site.