after burning the kodiak with the box fan behind it for a year, then the factory "loud" dual cage fan installed, I can sat the dual fan washes more heat.
the box did good but depending on the set up, it will vary. here its backed up to a 100 yr old stone chimney. The box tends to draw cool floor air and after careful analysis with hand temp probe, its 20% less efficient then the "bolted on" one. when crankin good the sides in the upper quadrant hit 500 +
The best addition i found was the prop rod I made from 1/4" round brass stock, bent a "z" bend to enguage the nut on the front right side of the lid.
the angle and thus the directed flow of hot air, penetrated the room so as to better disperse the heat more effectivley and actually made the upstairs warmer..
the best additional "radiator" for it is the porcilinized cast iron water vessel that the air flow also dissapates and thus humidity laden air "feels" warmer..
P.S. a speed controller makes all the difference with the fan noise also!!