Not sure about the specifics of a Carrier heat pump, but most of the automated thermostat manufacturers sell versions that work with heat pumps. I use a RCS TR40. This allows for three stages of heat. The geo unit is typically Stage1 and then most systems use electric toasters as the next two subsequent stages. My next stages are high efficiency propane furnaces.
The geo units are scaled not to handle the coldest of days so during the majority of days, the compressor is running almost continuous, but with less amperage for each hour, optimizing energy efficiency.
Some of the furnaces uses speed adjustable blower motors, which may require a "special" thermostat to send the "how fast" message to the blower motor. I suspect these motors could still be used with a non "special" thermostat, but then the variable blower feature might be omitted.
The reverse cycle function is typically not handled in the thermostat, but in the control logic at the furnace that uses "A/C" (yellow) signal from the thermostat to trigger the valve changes to reverse action.
eh, i dunno what a heat pump is, but it's a gas-powered forced air furnace if that helps.
Yes, that is helpful. What you have is a gas furnace. A heat pump is an A/C unit that works in reverse to generate heat (as opposed to remove it) as necessary. The operation is somewhat different, especially the multi-stage one with aux heat. Carrier's heat pumps can be used with any thermostat but they claim that that top end one can only be used with their thermstat.
I looked at the Aprilaire site and it seems strange that they don't have a compatibility chart. Did you ever find such a thing?