Mine looks like this:
The stove is the red star. The blue square is the location of the return duct. I cut a hole in the duct and put a 150 cfm exhaust fan in the hole. So there's no duct -- just a blower in a hole between the rooms.
Before: The room with the stove would be mid 70s, and the back bedroom would be maybe 58.
After: the back bedroom would be maybe 63. There's a big difference between 58 and 63, but I really though it would make more difference.
Blowing the cold air from that back room (middle top of the drawing) might make more difference overall in the house, but the big rooms on the left don't need the heat.
We bought a new house, so I'm just going to fix the hole in the duct and forget about it, but if I ever do something like this again, I'll be going with a bigger blower.