Kashgar, Tashkurgan, Kashgar, Hotan, Kuqa, places around Urumqi if you want more Kazakh/Mongolian/mountain experiences (the city itself isn't great), then Turpan, Hami, Dunhuang, Jiayuguan, Zhangye, Xining, Tongren, Xiahe, and Langmusi. I've been approximately along this route, and I really loved it and wish I had more time there.
After that you can do what I would have done if I had more time, and work your way slowly down to Chengdu via Zoige, Songpan, and Jiuzhaigou. Then Shangrila, Tiger Leaping Gorge, Dali, Kunming, then up to Chongqing and the 3 gorges, then maybe up to Xian and Beijing and by ferry from Tianjin or Qingdao to Incheon.
http://www.thelandofsnows.com/tibet-ove ... o-chengdu/
http://www.thelandofsnows.com/tibet-ove ... hangri-la/
For me the least interesting part of China is the East, and pretty much everything east of Xian wasn't nearly as interesting to me, which is why most of the above recommendations are in Xinjiang and traditional Tibetan areas.