Well, google does provide a detailed version of Chinese map, only in Chinese:
http://ditu.google.cn/maps?hl=zh-CN&tab=wl

It gives the zoom level from 0 to 17 as well, the url is like
http://servicetile.mapabc.com/google...=&y=%d&zoom=%d

In Canton, level 0 Guazhou city map block looks like
http://servicetile.mapabc.com/google...oom=0&s=Galile

It works exactly same as the English version google map, just with some url address changes. The coordination numbersing uses the same system.

The only thing you need is knowing Chinese to use it. If you don't know, a detailed version English map is useless anyway, since in China they don't label street in English and most guys don't know how to name street in English.