jdoskoch-
If you read through all the posts under stoves in that section of the Library, you'll get a real education on the pros and cons of the various types of heaters. Other than the Wallas, the Force 10 Cozy Cabin in propane and diesel along with the somewhat more advanced Dickinson 9000 propane fireplace are the most common choices. The Force 10's run about $400 on the Internet, and the Dickinson can be had for about $600. But you also have to add the propane supply and safety systems to this which can add $200-$400.
There's a Toyotomi forced air model, too, but it's a bit too much for a cabin the size of a CD-22 in terms of minimum heat output, and has to cycle on and off all the time. It runs about $1200.
There's also a simpler version of the Wallas without the cooktop, but at not a similar reduction in price. About $1400 in the box, as I remember.
You can also get a 1000 or 2000 watt generator and use an electric generator, but that's too noisy an alternative for some. But it's a super easy install that anyone that can plug a toaster in can do! And costs under $1000. ($800 for a Honda 200Ia generator, and about $100 for electrical busbar (GFI) and the heater.) The heater also plugs in great at the dock with an extension cord if you have power there!
It also may come down to what system your local marine dealers are comfortable and good at installing, and/or sell at their store.
The boys up in Alaska have got some really exotic diesel and wood stoves that will also burn coal, driftwood, whale and walrus oil, bear grease, dried salmon skins, black powder, and anything else that doesn't move fast enough to get out of the way and/or and you can scrounge up off the beach or forrest. You'll probably hear from them shortly. (It's getting cold up there, their boating season is basically over, and they've got a lot of time on their hands.)
Keep the Home Fires Burning! Joe.