The Harman XXV pellet stove has a vertical vent option that allows it to be attached directly to existing 6 inch stove pipe. Are there any other brands/models that have a similar option?. I am considering replacing my free standing small wood stove with a pellet stove and I want to use my existing vertical stove pipe/metal chimney system that I already have in place. I know I could cob together the rear exit of most any pellet stove with elbows and pipe size expanders and make a vertical system, but I'm looking for units that have factory optional attachment pieces made especially for a vertical vent system. Does anyone know of other units besides the Harman XXV that has this option?