yeah, my home is a bit old too. might need a new heat pump soon. 18 years old and very inefficient. I would like to put in a ground source geo-thermal heat pump. but the least expensive method of trench burial of cooling tubing might be impractical. that would leave drilling 3 x 150 foot deep wells, for a 3 ton system/. but that is more expensive.
oh well, a good 2 speed 14-17 SEER system will do good too.