I am assuming you also want to save fuel. You got a price of $4000.00. How did he size the boiler? The savings is maximized by a heat loss calculation. The amount of radiation in the home has NOTHING
to do with sizing a hot water boiler.
I would use an indirect hot water tank for domestic water use.
The outdoor reset control is a great feature. It changes the water temperature in the heating system to match the heat loss of the home as outside temperature changes. You can also find outside design temperature info there and other info.
For more info on outdoor reset controls see the link below.