Thank you, Mike and Matt. The house warmed up quickly this morning thanks to your taking out those three 'extra' filters that we mistakenly put in our vents, thinking they would help. Instead, as you explained, they overworked the furnace and prolonged the wait for warmth we endured every morning.
The fireplace functions well again, after you shut down the noisy, broken right fan so the left fan can function quietly.
See you next year!