I think a fan is an inefficient way to move heat, especially at a low temperature differential. Ducting would be more efficient, it moves more air from point A to point B without most of the energy going into mixing the air.
30 years ago I dealt with the same situation. I installed a copper coil in my wood stove just below the flue exit, it connected to an old water heater tank at the other end of the house using a couple of garden hoses. I machined a centrifugal pump and used a small fractional hp ac motor, probably 1/10 hp or less. It worked ok, but the pump was poor and the coil in the stove may have been undersized. Today I would use a Bosch 12v intercooler pump, I measured about .8 amps at 12v, about 1A at 14v. They also have a brushless pump used in the Chevrolet Volt battery and Corvettes.