I have not been to the camera shops in Beijing but have in Guangzhou. Might I ask what you paid for your black M7? I have been thinking about moving up from my M6 to an M7 but I find the prices here all over the place.
By the way, you dont want the 90 APO summicron. YOU DONT WANT IT. Here are some pics:
Its a terrible horrible lens (to your credit card) and you just dont want it.
All my friends tell me I need to go to wukesong to check it out, but what I really need to look for there is a repair shop for my poor yashicamat.