hello, i live in chicago and am trying to figure out what size furnace i need? i have a newly remodeled 1200 sq ft raised ranch, with 3 bedrooms. brand new windows doors and insulated exterior wall. what size btu furnace would work? and what is the difference between 1 stage and two stage furnace. i have had three different heating and air guys give me three different size furnace.1.75000 btu heil 2. 90000 btu heil 3.115000 btu goodman can you help thanks. im told that the goodman is not a good name brand, any truth to that? please help..