Our 16 yr old A/C died when we were at Disney in September 2006 so we decided to replace the entire A/C/ furnace thing in May 2007. After pricing everything,and I do mean EVERYTHING--- Sears, Trane, and companies we NEVER heard of...... we decided on an Amana unit, installed by our local furnace/A/C guys. The package went for around $7000 installed. Our electric bill was cut by 3/4 last summer....so much so the electric company owes US money!!! Our gas bill fell from a third to a half probably owing to increased energy costs. The temperature in the house stays much more constant than it did before replacing the units. And no more cold spots.......
By the way, we heat/cool 2.5 floors with 3700 sq ft of living space.
As for the heat pump, we looked into that as well but decided it would not be as efficient in our Pennsylvania winters. It depends on where you are and the size of the space.
Good Luck.........
Babs