I am pulling the trigger on a replacement wood-burning insert for my old smoke dragon. I am leaning toward Drolet 1500i or 1800i. I can fit either; my assumption is go with the biggest unit I can fit? I've triple checked the minimum opening requirements for the 1800i and it does fit. I live in Middle-TN; this is not my sole heat source and the unit will be installed in the downstairs den of a 70's split-foyer home. The home layout does allow for good circulation of the heat up.