Our 1900 sq/ft. home located in N.J. has a open single zone radiant floor system with oxygen barrier pex in the 1st floor (950 sq/ft. slab).
The 30 yr. old propane Polaris 100K -50 gallon heater needs to be replaced and we want to separate the DHW from the heating system during the process.
Home is well insulated with SIP panels, heating load 25K btu’s. The 2nd floor rooms have electric baseboard heaters which are needed only on the coldest days.
There are 2 bathrooms, dishwasher & washer.

The heating contractor advised that we could convert to a propane
combi boiler or a new Polaris 100 K BTU’s -34 gallon model using a flat plate heat exchanger.
We need advise on options & models for wall hung modulating combi condensing unit vs buying another Polaris.
 The utility room has very limited space. 
Thanks,
Brian