I have a choice to install an air handler in my attic or gas furnace (as back-up heat) to go with my XL16i heat pump. Trane boasts that their top-ot-the-line air handler has 12 speeds while most other brands have 3 speeds. My question is: (1) Is the blower in the Trane air handler used in their XV90 gas furnace (2) Is the XL16i 2 stage cooling and 2 stage heating (Trane website talks about 2 stage cooling without saying anything about 2 stage heating)? (3) Is there a Trane zone control system on the market equivalent to the Carrier Infinity Zone Control Module, Infinity Damper Control Module and Remote System Access Module if not what is my best non-Carrier option for 4 Zone residential application? Thanks.