So I finished reading Lonely Planet's Guide to China.... all 1000+ pages of it. And have determined that China is a much vaster country than first imagined when the average train speed is like 25 km / hour. So the China part of the tour will have to be curtailed. Other than Beijing and Xian (terracotta warriors are there) and a few day trips on the side, I think we'll skip the western portion and just fly to Central Asia - it will cost the same as week or two of travel.
Next on the reading list is The Silk Road by Rail.