I certainly understand your situation... It took everything I had to buy my
house. So been there, done that!

It sounds to me like heating your house is going keep you "broke" from now
until eternity!

So I would look at this long term - what is best in the long range of
things?

I think energy rates are going to keep going up, up, up. So I think the
thing to do would be to eventually install double pane "Energy Star" argon
filled windows in your house. This will *drastically* reduce your heating
and air conditioning costs. And also you should eventually insulate the heck
out of your house.

But this will cost a lot of money, and if you are constantly paying high
heating and air conditioning bills, you may never have the money to make the
improvements...

So what I would do for now is to get the largest heating unit you can get,
and zone the house out. Instead of heating the *entire* house, figure out
which rooms or which portion of the house can be heated while leaving the
rest of the house unheated. (Close doors.) Perhaps you can move your office
elsewhere for the time being?

Then just heat certain rooms or a certain section of the house. This will
save you money on energy bills for the time being. Then maybe you could have
one window replaced a year with an "Energy Star" window - this will be
expensive. Eventually when all windows are replaced and the home is well
insulated, your heating requirements will be much less.

Then you should be able to heat your entire home for a more reasonable cost.
And at that time, you will not need such a large monster furnace!

Here is the Energy Star web site...
http://www.energystar.gov/