I have a 1939 Heatilator fireplace, and I had a BK Sirocco 25 installed in it. I had a CSIA certified chimney sweep install it, and he had to cut out the steel top of the fireplace in order to get the new steel liner down the chimney. It was apparently a very time consuming job, as that steel in that old Heatilator is very thick.
My stove dealer gave me a measurement sheet to fill out, and the Sirocco was the only one that would fit. I really wanted the Princess, but I am very happy with my Sirocco.
My little house is about 1300 square feet, and the fireplace is in the living room on the main floor, above the hot air furnace in the basement. Here in Newport we burn fuel oil, and my furnace is 20 years old so I have to replace that big daddy this summer, but it does keep the house relatively warm when I don't have a fire going. (I have yet to restore my original double hung windows.)
Just opposite the fireplace are the open stairs to the second floor, and the fan on the Sirocco does very well in pushing the hot air upstairs. The chimney goes through the master bedroom, but the BK really does keep my little house toasty, even in the upstairs rooms on the opposite side of the stairs.