Building new house. 4500 sq ft. Each side of house will be controlled by separate HVAC systems. Contractor has recommended Coleman 5 ton 18 SEER split system with 110,000 BTU (Model AC8B048FC34T18S condenser; Model FC62D3XN15T coil; Model TM8X100C20MP11 furnace) for one side of house and Coleman 4 ton 18 SEER split system with 90,000 BTUs (Model AC8B036FC34T18S condenser; Model FC483XN15T coil; Model TX8X100C20MP11). I favor upgrading to a two stage system 9T, 9V or 9M-12. I also wonder about upgrading to CP9C at 97.5% efficiency. We live in southern New Mexico so the winter can be cold but typically isn't very long so the higher efficiency heating won't likely be recouped in energy savings in any reasonable period of time but the better air conditioning should. Also the better systems have quieter fans and better components (or so I've read) and the quiet is very important. Any advice would be appreciated. Also the estimate for the whole job is running in the$$ range --without the complete details, I know it is impossible for you to be precise on an estimate -- does this seem like it is in the "reasonable" ballpark?