What is the current standard build?
After browsing the hardware forums I found a standard build from March of 2013, is there a newer standard build?

I'm currently set on 4 x 7970's, I'm not set on anything else. This build will be rack mounted ideally.

Any advice would be appreciated.
things haven't changed much since then. are you looking for something for personal use, or for professional use?
most of the advice you'll find on the forums (including advice i provide) is largely using desktop hardware, which may not be ideal for professional use.