While I still stand by going for a stove rated bigger then your square footage, I'm by no means knowledgable about what I'm saying. I have a good fire going in mine, and it heats my living area very nicely. Basically I can get 20 feet or so around the stove hot enough to wear shorts and a t shirt when it's freezing outside. Go farther back into the house and it's cool enough to sleep with a blanket on.
I dont think it's so much how big the stove is rated for, but how big of a fire you want and will enjoy. I can get mine a whole buch hotter if I want, but have found that once I get it going, adding a log onto it about every hour or so, depending on the size of the log, is plenty.
I carry in one load of wood in a canvas sack for the day, and never burn all of it.
Here is the manual for my stove. There is all sorts of good information on stoves in there that you might find useful.
http://www.napoleonfireplaces.com/Tech/installation_manuals/EPA.pdf
Eddie