Honestly IMO a 50cc saw would supply any house with wood heat. Yea yea yea I know you can't see how anybody would get by with a 50cc saw cutting this big wood. There's the catch this big wood...just pass it up and cut the wood the 50cc saw is comfortable with. There is plenty out there you just pass it up so that you have the reason to run your manly saw. I'm guilty of the same thing myself. I used to vote 70cc but with time and age on a guy that works for a living my vote goes to the 50-60cc saw for all my wood up to 20-24'' wood.
What we have here is wisdom. Great post.