Can I pair two thermostats to work with a single zone system?
What you actually need is a single thermostat that has support for one or more secondary remote thermometers.  I believe the Honeywell TB8220U1003 supports this via this part:

Remote Thermometer http://customer.honeywell.com/Honeywell/getliterature.axd?literatureID=C7189U_color_3in.jpg

As a side note, it is often necessary to properly balance your HVAC system depending on the season by adjusting the dampers to increase/reduce the airflow to certain areas based on the season.  Also remember to open your cold air returns in the winter.  You might not need a different thermostat at all!