As regulations are changing, I've been watching closely to see if any new designs will be hitting the market. So far, just about all new furnaces are very similiar. Tonight while browsing the web, I found a new model from usstove. It's an Ashley AF700, and appears may be a replacement for the Hotblast furnaces? I couldn't find a manual, but I'm curious on its design .
I purchased the Tractor Supply version of this stove. It's model number is CF700M and it is called the Clayton (sells for $1,300 which is considerably cheaper than the Ashley). I now have about 7 burns in it.
I like the furnace, but had to make modifications to it. I replaced a US Stove Hotblast with this stove, so will make comparisons between the Hotblast and the Clayton.
The specs on the Clayton says it will handle 24 inch logs--it is more like 22 inches for a comfortable fit.
The two 8 inch hot air vents are closer together than the Hotblast, so I had to make modify where they are attached to the plenum.
There is no air intake bimetal thermostat on the Clayton as there is on the Hotblast. Instead, there is a hinged louver. I think the reason is that, to meet EPA specs, you can't really starve the stove of air. There is a screw adjustment to this louver, but there is enough resistance on the hinge that I can just open and close it by hand (using gloves). I put a wood stove thermometer on the exhaust stovepipe. Even with the louver all the way open, the stove doesn't get that hot as the thermometer barely entered the normal range, so it seems safe to use even if kept all the way open. I can't really tell a lot of difference between when the louver is all the way open or closed. When starting the fire, however, you will want to open the louver all the way.
I fired up the furnace outside first. This burned off the paint and other fumes before bringing it inside. It would get pretty nasty if you brought it inside for the first burn. The user manual recommends this.
Once I got the stove installed inside, I installed the fan motors and fired it up. There is a thermodisk attached to the back of the stove that activates the fans at a certain temperature and then turns the fans off at a lower temperature. This the same arrangement as the Hotblast. With the Clayton, the thermodisk kept cycling on and off. Apparently the cool air being sucked into the fans cools down the thermodisk enough to shut off the electrical connection. I called tech support and they said the fan needs to be enclosed so it is drawing hot air off the stove. There is no reference to this in the user manual. I welded up a frame which encloses the back and top of the stove. I also encased a 10" by 2' galvanized piece of duct around the stovepipe to suck hot air coming off the exhaust stovepipe down into the fans. It works great. The thermodisk happily keeps the fans running. It also releases much less heat into the room where my furnace is located than my Hotblast. I also installed a frame for a 20" by 24" pleated furnace filter into the enclosed frame. It sends much hotter air into my plenum than the Hotblast did. My guess is that it heats up my living air about 30% faster than the Hotblast.
As far as efficiency goes, I'm probably using half the wood for an equivalent burn. I would be careful opening the door to add wood when the stove is at full burn. (I could do this with the Hotblast) When I tried this, the flame came out the opening. However, there is no problem if I let it die down to coal before opening the doors.
Would I buy it again? Yes. I think it is a great furnace and a definite upgrade from the Hotblast.
I don't have much tolerance for fools anymore "My clutch never slipped until you changed my tail light bulb" 
seriously. lol