We now offer ECM variable speed and PSC multi-speed hydronic 2-pipe air handlers on a special order basis.  Ideal for both hot water heating and chilled water cooling, air handlers are often the best way to offer central forced air.  The benefit of using a hydronic air handler over a DX or refrigerant-based air handler is that the heat pump is not affected by indoor airflow, multiple zones or un-matched indoor and outdoor capacities.  For example you may have 5 tons of hydronic floor heating throughout your home and garage butonly need 3 tons of forced air cooling and dehumidification using a ducted system above grade and not in the basement.  Perhaps you would like to use more than one air handler without wanting more than one heat pump outside.  Alternatively you may want floor heating in the basement, garage and main floor of your home but to use forced air in the bedrooms upstairs for heating in winter and cooling in summer and only cooling on the main level during the summer.