Without knowing a lot more details, it is a little difficult to speculate. I think if the stove and stairs are close to the middle of the house, I would put two power vents as far apart and at opposite ends of the house. These would draw air to the ends of the house, push it upstairs at the outside and the cooler air would come down the stairs to the stove. Yes, some warm air will go up the stairs too, but whatever volume you can push through the power registers will return down the stairs. Higher velocities will maintain a more even temperature up and down.