As darthviper107 said above, although i7-5960x is xtreme edition of high end class cpu, it is still in consumer class, and it doesn’t support dual cpu config or quad cpu config.
I think 5960x is enough for you to build light. However, in pure math, dual xeon 2660v3 still beats dual 5960x
You can do the math here: CPU frequency * CPU cores * CPU number = its/their power (HT and Turbo doesn’t count)
You can use this equation to compare with CPU’s with same architecture and same lithography:)