Shopping for propane furnace. Do not have chimney. Have 2000sf on two levels and 1000, sf walkout basement that is used as office/recrreation area. Considering 90,000 btu Amana Air Command 90 Ultra Efficiency. Also have availability of 90,000 btu ComfortAir at distributor price point, +10%. What are most important factors? Current furnace is a 75,000 btu comforttherm that is then years old. Has cracked heat exchanger. What are critical factors in making decision besides price.