How cold do you get? We're similar to been's climate. 2000 with average insulation and windows probably would do just fine on 60K 90+ here too. Sis has 2400 sq ft 2 story, decent insulation, leaky windows, uninsulated crawl and heats to about -10° out with 75K 90+. Below that it loses ground. Bigger isn't better.
Also dealers need to look at duct sizing. Today's 90s do not like a high temp rise. They are quick to shut down on their limit switch with a borderline sized duct system. These $3 limits tend to stick open if they have to open much.