Green Mountain Fireplace is where I bought mine. I know that Green Mountain isn’t much to look at but If you go with the Enviro, I would strongly recommend Green Mountain. Also the people there are great to work with
What’s crucially important is that this stove has the current convection fan. The new style fan comes with a capacitor, it is louder than the original BUT it moves a ton of air an in this case it is great if you need to heat a large amount of square feet. The M55 when it was sold with the original fan made this unit one of the quietest stoves around. Unfortunately, it was a design flaw....It couldn’t handle the heat output of many Pellets and was prone to constant overheating and shutdown. For a while, Enviro replaced this fan with the new style (under warranty) You don’t want this stove with the old style fan
! Maybe one of these two outfits will work a deal with you on the new fan. Many current M55 owners will agree with what I am telling you, and there are reams of old posts on this very subject. I don’t know anything about the Mt Vernon but maybe some folks here will give you their best comparison.
Good Luck, Bill