I have the SCF-050 and it heats my 2-story farmhouse in SE MN with no insulation in the walls. In below-zero weather I sometimes have to supplement a little with the propane furnace, but mostly not.
Nice unit, seems well built. Fairly easy to clean, and easy access to parts that may need replacing over time. It is a 40,000 BTU furnace if I remember correctly, and I don't do any night-time setback (lower temperature) like I used to with propane, since it takes too long to catch up again the next day.
-- Dave