I have a Rheem heat pump with auxiliary and emergency heat. My current thermostat is a Seco TA-2000 with the following wiring configuration: B W2 X R G and a piece of wire connected between E and W2. There's also an orange wire that's not connected to the thermostat. The Honeywell manual does not address this situation beyond referring me to a heating / cooling contractor. My terminals on the Honeywell thermostat are as follows:
E Aux Y G O L R B C. Can anyone tell me the correct wiring configuration? Thanks.

Have you looked under the sticky notes at the top of the page. Might be something in there about the letter/color change