Good advice from Joseph, load calculation is first step. I'm a huge fan
of variable speed furnaces. They reduce your electricity consumption
and if matched to your home with proper calcuations will push air longer
which may help in reaching the second floor. You can buy them in both
80% effecient models and deluxe 90+% models which will save on gas
consumption too.

There comes a time in the affairs of man when he must take the bull by
the tail and face the situation. -- WCF
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