ok, lets get the basics up for the discussion. 1) your best bet will be to use steam and not convert to hot water as it would involve replacing the radiators. 2) you have hard water. this will probably require a water treatment(please give suggestions) to avoid some of the problems. 3) I bought a house (3000 sq ft- 120,000 btu net furnace output, and had gas hot water heat plus baseboard with 5 zones installed fo 9k. 4) Most of the super efficiency systems are likely to give you more problems initially(just because they don't have a long track record). 5) I called about 8 heating contractors to get 3 bids. Before you bring anyone out, make 2 lists: 1 what you NEED the system to do, and 2) what do you WANT the system to do. This will help. Also get DETAILED QUOTES. If you don't see something on the quote, you won't get it(experience). 6) When you get quotes for replacing the boiler, insist on seeing their heat loss calculations(look for any that are real high, or real low and avoid them, or at least question it).