Xeon cpu's are best for server applications not gaming, the 3970x is only 15% better then the 3930k for double the cost. In my opinion I would just go with the 3930k but if you have to go with the 3970x
Xeons are not just for servers. The lga2011 i7 6-core are actually the same dies as the lga2011 6-8 core xeons. The only reason to go with xeons is for multi cpu configs since i7 only support single cpu configs. You need to be more specific on which renderer you are using and how much you want to spend.