I want to obtain at least 16 SEER cooling, and prefer a Trane or AS system. Actually, an AS condensing unit would be preferable because of the vertical discharge, for avoidance of turbulence that might be generated by the Trane angled discharge in the walled-in but well-ventilated area where the 4 condensing units are located. Putting these considerations together, I come up with the AS Allegiance 20 commnicating condenser coupled wth an AS 4TEE variable-speed air handler (that's an air handler intended for a heat pump, but would be installed with a hydronic coil instead of strip heating elements).
I don't have the heating load number handy, but the existing coil in a Magic Aire air handler is a 3-row unit that has provided plenty of heat. I haven't identified a suitable Trane or AS hot-water coil, but there are at least several custom coil manufacturers who will fabricate a hot-water coil to an exact fit for any air handler.