Watching this thread - here's what I'd do - which incurs minimal costs as I see it.
Run a SS flex liner through the existing flu pipes. Given the size you stated I doubt there'd be an issue.
Here a vid on youtube that shows a Stainless Steel Flex Liner install.
You do NOT need to do the wrap piece that they show.http://www.youtube.com/watch?v=5OIcxRdb6Rs
You can find the SS Flex Liner in kit form where they include necessary clamps and tops/flashing etc on ebay.
I did one at my parents house - through an old brick fireplace - and attached a wood insert (a wood stove not free standing).
The 25 foot kit cost under $400 including shipping.
You could of course stick with a stove that utilizes a Electric Power Vent - but then - well - its using electricity any time you are using the stove. It's great for certain circumstances. In your case...if it were me I'd throw a wood stove on the upper level and a coal stove on the lower level. I run wood,coal and in the past pellet stoves - all in a single heating season - as it gave me options and flexibility depending on what I had and what the current prices were for the fuel.
Another vid - this shows a coal stoker - lots of electrical gadgets !
But then thats the cost of convenience.http://www.youtube.com/watch?v=54HXhXv9 ... re=related