Good post Edwin

To the OP - to help contain the heat downstairs you could add a curtian
at the top of the stairs. Still that space heater is a bit small for
that room. Can you add a gas fireplace? I know its a lot more $$$ to
install but will be cheaper to operate. If asthetics is not an issue
and you application and circumstances would alllow you could add an
unvented propane or natural gas heater that mounts to the wall.

I have one from Charmglow in a cottage.
Here is a model that looks like a wood stove and will heat that spice
very nicely. Its LP so you could use a gas bottle from your BBQ grill.
Just a small hole to outside where you place the tank.
http://www.homedepot.com/prel80/HDUS...hR esults.jsp

Search the HD site for Charmglow to get other options.