Thanks to all for the suggestions of domestic furnaces 
models which would likely save some money, but...

compulsive shopper that I am, I had already checked out the
Suburban and Hydroflame units, and they are mach larger- 
literally three times the volume of the Propex Compact 1600
(14"x6"X4.5"- a furnace the size of a five pound box of spaghetti!)
With the smaller Suburban line, when you go to a lesser BTU capacity, 
they just change the burner unit, and maintain the same 
physical unit size. Also, my wife looked at the Eurovan Winnie
furnace, are reported back that it was also pretty big.

The other pluses are the happy listees using the Propex already,
and championing its low propane consumption and easy installation.
 
...and as for the Coleman catalytic heater and the
open window, I saw a listmember light one of these 
off a couple of weekends ago, and that was the defining
moment when I decided I wanted a permanent, fully
vented furnace- and a CO detector to boot!

I'm going to call Propex tomorrow. Fence sitters, let me know!

Tom F.