Hot Water Boiler & Solar heating

Has anyone installed a Hot Water Boiler (i.e. for heating and for hot water needs)? Any brands you can recommend? I've heard "Trinity" is good. Also, I'm looking at setting up a water-to-air heat exchanger from the boiler to my existing forced air furnace, if it's possible. That way I can use the solar hot water panels I'm planning to install to heat both the house (via forced air) and hot water needs. Any advice anyone can provide on this would be really helpful. Where does one find water-to-air heat exchangers? How hard might it be to retrofit an existing furnace with this? Thanks.