As a lot of other posters said, shop around. Get two more bids.
Carrier and Trane are both excellent brands but there are others.
You said your heat pump lasted six years? That’s not right, you may not want to do business with whoever sold you on that deal because heat pump warranties are usually 10 years.
Any-who, the heat pump/propane system is a little exotic. It will lower your bills but you may or may not want to make the extra investment.
Some questions to ask the installer and yourself:
What is the payback in years for the system?
How much longer will you be around?
Is the house otherwise well insulated and draft free?
How is the duct system?
What is wrong with the current furnace?
If they say the heat exchanger is cracked, make them show you with a carbon monoxide detector.
Maybe you can have the furnace repaired for a few hundred dollars.
Maybe you can have a reasonably priced furnace installed for about $2K.
Good advice and good questions. Thanks.
Have been very pleased. Live in a Pittsburgh-type climate. Standard Carrier heat pump thermostat allows auto switchover from heat pump heating mode to gas furnace at user selected outside temperature.
System has worked very well. Also got reduced electric rate from local electric company since heating was "dual fuel"