New hydro-air system design discussion

SethE

Hi Everyone,
I am looking to replace my current 20 year old hydro air system with something new and far more efficient. I'm currently in the design phase. Here are some of the basics of where I am now.
-3400 sqft house
-3.5 ton Trane AC/Air handler for the 1st floor, single zone (likely over sized for 1650sqft)
-3 ton Trane AC/air handler, 2nd floor, 3 zones
-Weil-Mclain WGO-4 boiler (126,000btu), Oil, chimney vent, connected to the two air handlers
-The system originally had a 80 gallon indirect hot water tank, but that has been replaced by an electric heat pump unit.
-The attic space has been super-insulated to R-60

Here is what I'd like to get to:
-Replace the AC/air handlers with Heatpump/Air handlers
-right size the system(s)
-Open to the idea of moving to gas if it has big benefits.

What are my options? Here in New England we have a few cold winter months, but I'm interested in running the AC units as heat pumps during the more moderate times of the year. I am looking at options from Carrier, Bryant, etc, but I am not sure if some of these new heat ump systems will work with a hydro-air system.