Help!! I'm so confused with AC tonnage for my new home. I'm loathe to replace the furnace which is new and rated for a 3.5 ton AC. A couple contractors recommend a 4 ton AC unit but have concerns about the blower capacity. Will a 3.5 ton effectively cool a 3700 sq home? Especially the second floor? I know it depends on alot of factors...but generally speaking, is that sufficient?