I would recommend a hawken, I have had one for the last 3 years and the only problem that i have had was i heard a noise comeing from the motor for a couple minutes and it was quickly replaced by hawken no questions asked, I also noticed that the black stuff comeing out of the furnace by the door turned you off from hawken if you look under the central tab there is a post there that a guy with a central has the same issue. Burning greenwood will make this happen with any furnace. Dont be misled by one guy that is impatient look at my post under buyer beware and maybe that will make you reconsider.There is only one thing that i had to modify and that was add anouther batt of insulation in the back to cover up the pumps once they were installed. When i was doing my research I looked at a few different things such as I wanted legs so i would not have to pour a concrete slab,I like the 4 points of adjustment on the door, the firebox design. keeping heat transfer and dead spots in mind, I work for a concrete company and we use a boiler system to heat the water that makes the concrete in the winter months and their setup has never had anything different than round also i looked at old steam locomotives and their fireboxes have always been round also so to me that said that it had stood the test of time. Also corosion is something to think about too if you have any dead spots or flat boxed spots where sediment can be trapped in chances are that is where it will start. Forced air i like ,my buddy has a central with natural draft mine has a forced air. We have basically the same setup he might have 30 ft more of underground, his takes alot longer to get to temp with a whole lot more smoke, as for wood consumption i would say that mine will last a little longer his stays burning a whole lot longer where mine seems like it gets the temp faster then shuts down. We both like our owb's and are very happy with their preformance. And i am very happy with hawkens warrenty and their quick no questions asked response to my problem. Also read the warrenty before you buy it seems like all are pro rated but some only cover the firebox for a very short period. Good luck
Tim