this sounds like your levels are well insulated from each other.

I don't think you will gain anything with a Cat stove unless your plan is to go to a much smaller stove and move the heat better, the Quadrafire burns clean as a cat but without the cat and cat maintenance.

a vent to the upstairs if you have a place you could get from the main room downstairs near the fire to the upstairs and put a grate on it. it might be your house is too well zoned with no good ways to move the heat around

I am heating a much less well insulated house in a colder climate with a smaller stove
but being that would heat was what the house was designed around with vents places through the floor the heat can get around it works.

it sounds like you have a great exterior envelope but that it might also be dividing your floors up with no way to get good convection and let the heat rise upstairs.

cutting a vent might save you a bunch of money on a stove.

Yes GCPete, after finishing my basement the Sheetrock ceilings down there stopped allowing heat to radiate through the floor upstairs. I may put something like a bathroom fan and pipe it to the upstairs. I may cut registers in floor to allow for natural rise as well.

not even sure you need a fan , the house my great great grandpa built has a trimmed in hole near the ceiling in every room down stairs and a vent up to each of the 3 bedrooms upstairs

there is a rubber backed rug in each bedroom , when company comes over to spend the night the rug is pulled back and that is all it take to warm that room right up.

one stove in the corner of the house keeps it all warm

Wow! She must be hot!

Nope, always cold.