Outdoor wood burning furnace ???

I will be purchasing an outdoor wood burning furnace to help heat water with in the near future. I am looking for feedback as to which one seems to be the best. There are so many different manufactures of these furnaces on the market. I would like to here from anyone that is using one or knows of a friend that is using one. I am looking for issues like length of warranty, stainless v.s. steel, max burn time, problems or replacement of parts, ease of cleaning, how well and how fast it heats up. Overall likes and dislikes, and the make and model of the unit. They seem to be very popular in the northern states, and from what I have heard, they really help reduce the heating fuel bills. Any and all input is welcome. I will be installing the unit in central Texas, and it will supply hot water year round and maybe radiant underfloor or radiator heating for winter months, in a 2600 sq ft. home.

captarcandspark