I was torn between replacing my builder�s grade York system with a Lennox or Carrier furnace and a/c's in a 2-zone home and decided on the Lennox. I had a 2-stage, 80% furnace and one-stage 17-seer a/c installed on the lower-level of a 2550 sq.ft home to cover the main level and basement. I was supposed to have a 2-stage furnace and one-stage a/c installed for the upper-level. After the installation, I was informed that they installed a one-stage furnace on the upper level and that Lennox does not make a 2-stage of the size I needed (45,000 btus). To make up for not letting me know this upfront, I am being offered different options:

1--Leave everything as is, install air scrubbers and provide duct cleaning for both systems.
2--Install a Carrier 2-stage furnace to the attic (leaving the one-stage Lennox a/c and coil); provide duct cleaning for both systems.
3�Change the 17-SEER a/c on the lower level to a 21-SEER and change the a/c on the upper level to a 17-SEER heat pump

I generally prefer to be warm than cold (higher heat in winter, less a/c in summer). I keep reading that 2-stage a/c is more comfortable, but I am not sure if those opinions are from those who like temps at 65 degrees vs. 74. I also struggle with low humidity in the winter months. I read that heat pumps are better from a humidity standpoint, but not for warmth.

Would getting a heat pump and keeping a one-stage furnace be essentially the same as creating a 2-stage system? Would a heat pump and a 2-stage furnace actually create 3-stages? Which is better: 2-stage furnace/1-stage a/c or 2-stage furnace/1-stage heat pump or 1-stage furnace/1-stage heat pump?

Any help sorting this out would be appreciated.