If I may add my 2 grains of salt here. We manufacture wood stoves (lot of them) and we use the Sq Ft rating and this is heresy on my part but I hate the Sq Ft rating for stoves for the following reasons:
1) It's up to each MFG to decide what to rate their stoves at
2) There is no lab or scientific protocol to test this and no agencies to monitor and certify this rating.
3) Some MFG are ridiculous in their rating (over 3,000 to 4,000 Sq Ft!). Gimme a break
4) A wood stove is a 'zone' heater, not a forced air furnace. it has no means to transport the heat from one side of the house to the other. If you put a wood stove in a closet and close the door you will have a warm closet... no more.
Unfortunately, customers really like the Sq Ft rating and we all follow suit. A better baseline is the cubic foot of the firebox ( a small stove is a little over 1 cu ft and a large one over 3.0 cu ft.)
Some people will buy a specific model and claim it heats their entire 1,500 ft house. Other people will buy the very same model and say it doesnt heat their 1,000 Sq ft house. It depends on your level of insulation, air movement, ceiling heights and too many variables to mention.
When choosing a stove placement is more important. If its on the main floor with open space it will be easier to radiate heat. If you have cathedral ceilings makes sure you have ceiling fans turning slow to move the ambient air.
In case of doubt you can always go bigger and once your stove is up to temp you can choke it down and it will cruise slower. Also do smaller re-loads if its too much heat.
Ask away if you have any questions. Which models were you considering?