I did this tour last year with Yangtze add on. The amount of money to take is really dependent on how much use you make of the many opportunites to buy souvenirs. There are some very beautiful things - silk, cloisonne, paintings, etc. Also more most merchandise. Just be aware that drinks in hotel bars are priced at 4 star European hotel prices. However, all meals and entry for visits is included so you don't need cash for that.
Hope this is of some help.