New to the boards and really appreciate the expert advice here.

I want to retrofit a heating and central air system into an older shore house. The first floor is accessible from the basement, where there is a nice sized closet to hang a furnace unit. The second floor is more difficult, needing ductwork through first floor closets etc.

The house is 1800 sq ft with plans for a 500 sq ft second floor addition in a year or two.

I have received several bids from very reputable contractors and am having trouble comparing apples to apples. Some suggest a single-zone system using American Standard products with ducts running through the closets. Others say a two-zone system is the way to go, but unclear where they can put a second unit upstairs (there is no attic). Still another suggests a single zone downstairs with a ductless system in the upstairs master BR.

How do I determine the best way to go? Is the number of zones determined by square footage (ex, if over 2000 sq ft, so with two zones or something like that)? I am reluctant to do a ductless unit upstairs, only to tear it out next year when I do the addition.

Finally, how best to compare brand names? Some bids go with lower-end products (Weather King by Ruud, for example), while others insist on American Standard. I don't know enough to pick the right brand for my situation.

Pls understand I am not looking for anyone to select the bid. I just need advice on what I should be looking for and the best way to make the decision. Thanks very much for any help you can provide!