Simple question, the best small museum in Stockport?
Stockport Story has a lot in it, with lots of good temporary exhibitions including a Lowry painting.
The video about the battle of Coombs in the Stockport Story (by the side of the market hall) is just about the best one I've ever seen in any museum and never fails to cheer me up. Local school kids act out the story of the battle between the Celts and the Romans, dressed up in tartan blankets, table cloths and cardboard breast plates. I challenge you not to burst out laughing when they prepare their human sacrifice by force-feeding her Ribena. The screen is just through from the entrance in the room dedicated to the iron age history of Mellor. The rest of the museum, while not half so funny, is well worth spending an hour or two looking through and it's all free.
There's a charge to enter Staircase House but well worth it, each room is set in a different age so you learn a lot about the history of Stockport.
While not a museum, Chadkirk Chapel and country estate near Romiley can provide a lovely afternoon out. The chapel is open at weekends in the afternoon and serves drinks and biscuits. Lots of woodland walks and a beautiful walled garden. Look out for the grave of the man struck by lightening.