Thanks so much for all the responses.
Toddy, haven't heard of the HeatStorm, I'll check it out.
Meadowlark, I do have storage space in the area where the furnace would go. Haven't completely rejected the idea of having furnace installed, but I'd hate to give up the storage. Also, plan to do lots of boondocking (done a fair amount already), and my understanding is that lots of DC power is required to run the furnace fan. Thanks for the welcome!
JerryC, I don't know how old the Wave 3 is, or how much it has been used. Could be, indeed, that it needs cleaning or replacing.
Dutchman, my Wave 3 is mounted to the wall next to bathroom door, with a fixed copper (copper-looking, anyway) fuel line feeding it. Other than when sleeping, though, I spend most of my time in the rear dinette area, far away (relatively speaking) from the heater. I don't have legs for the heater, but I believe they sell those separately. Your post gives me the idea of getting legs and a flexible hose, if possible, that I could connect to the fixed fuel line. In colder weather, then, perhaps I could detach from the wall and move the heater around as needed. That might be the thing to try before moving up to a Wave 6. Thanks for the input.