Craig,
There is a few things to consider when you are picking a boiler.
First is the size of the house. Some boilers are available in one size only. It may not be the right choice as it could be too small (meaning you are stuffing firewood into it all the time with little heat gain) or too large (you cannot sustain a hot fire to prevent creosote build up or a potential chimney fire).
What type of existing system pressurized or unpressurized. This will also make the difference with the boiler type and how it needs to be installed.
Do you have a storage tank? Depending on the boiler system this is usually a nice to have as you can sometime fire up the boiler as little as twice a day, sometimes once a day and in the shoulder seasons sometimes once every few days. (This is also needed if you are going from one system to another ie. pressurized system to unpressurized system) Also this is where the domestic hot water (tap water) coil is stored unless you plan on keeping your existing boiler and using the wood boiler as primary and the propane system as secondary.
Next question is the efficiency, most good wood boilers will have a gasification system within the boiler. This is where the wood smoke and the volatile gases within it is also burned to gain more heat energy ie. you can use less wood!
As for price....well yes you are right boilers are expensive! The better systems I see start at around 6K then if you do it right with the storage tank, chimney, and installation it could end up being a 15 - 20K project. HOWEVER... now you need to take a look at the energy savings. Find a good fuel cost calculator such as this
one and plug in your data. Then you can figure out your savings and how long before you see a return on your investment.
As for boiler manufacturer....that depends on if you want an indoor or outdoor boiler which raises a whole bunch of questions.
You best bet is talk to your plumbers and stove guys. As a former stove guy I had these questions all the time.
Good luck!
