I put the 25000 btu empire direct furnace in my wheel house and haven’t regretted it for a second. My house is 6.5 x 14 and is spray foamed so it’s quite easy to heat and the furnace rarely works hard. One time on Red Lake on a weekend trip with the wife and kids it got down to about -25 and the house stayed nice and warm.
One thing I did you modify mine a little was installing a 12v brushless computer fan behind the front cover to circulate the warm air and that helps a lot. Empire offers a fan option that mounts in a similar fashion but my $5 computer fan is quiet, still moves a lot of air and has very minimal battery drain.
Also, I would definitely recommend direct vent just for the lower moisture levels inside the house. Likely one reason you are considering it but I also sleep better knowing it’s vented outside.
It’s an added expense to upgrade now but cheaper than going with the smaller unit and then having to change it out later