No one has mentioned the non-gasser made by Buderus. It's a good, simple, heavy boiler that's about half the price of a gasser the same size. You can download all the installation manuals and specs at the link listed below. If you need help finding one give me a jingle. I know some people there that can get you pointed in the right direction if you want to pursue it.
(broken link removed to http://www.buderus.net/OurProducts/WoodFiredBoilers/G201/tabid/607/Default.asp)
(broken link removed to http://www.buderus.net/OurProducts/WoodFiredBoilers/G201/tabid/607/Default.asp)