So I think I am going to install a Trane XL14c for a replacement for my Carrier 48SS.

Couple of questions...

I currently have a zoned system. The zoned system does not have a static bypass. I realize I'll need one for this install. However, the installer is telling me that I will need a modulating (electric) bypass damper since the fan on the unit is variable speed. Is this a correct statement? I have a really hard time trying to find this type of bypass ducts online, so want to make sure this is a valid point. He is also requiring a freeze control sensor. Is the bypass controlled by the zone controller? Its looking like I have to replace my entire zoning system.

Secondly, on the scale of low-middle-high, where would you classify this unit as far as quality and build? He will let me bump it to the 16 seer for not too much more, but not sure if I would benefit from that. (i'd say how much, but that isnt allowed apparently).