If you have over sized cast iron radiators, and you improve the insulation and air sealing in your home, you may be able to use a water to water geothermal heat pump with your hydronic system. At least for most of the winter. If you are set on tearing out your boiler and radiators, so be it. Just realize, that old does not necessarily mean inefficient. These old systems combined with modern technology, can be the most comfortable and efficient systems around.
Originally Posted by kjander