I think rue au Maire is an ok place to stay in terms of location. Had no idea that area was "heart of the oldest Chinatown in Paris." I've stayed near there and walked through it numerous times on my last visit in November. I wouldn't call that block particularly charming and agree that you should take a walk down the street with Google Street view and see what you think. I think you can find apts located in more charming areas.
Rue au Maire is probably better now, because I walked up it about a month ago and they were in the process or repaving/pedestrianizing it. I doubt that Street View has the latest photos for it.
