I really really need advice on replacing my 23 year old system. I am looking at a Rheem Classic 14 3 1/2 ton AC with a Rheem Criterion II Plus 2 two-stage 80% furnace. My current AC is 3 1/2 ton. The house is 2400 sq. ft. with 3 floors (including basement). The contractor thinks there is a ductwork issue, and he is probably right, but I am on a budget and can just replace the system. Is the Rheem a good choice, or would Trane or Lennox be preferable for some reason? My ductwork won't handle a variable speed properly, according to the Rheem contractor. Any advice would be greatly appreciated.