This involves replacing the processors with Dual 6 CPU’s which you can now get for around $650 (or less for a slightly slower model) installing dual SSD’s for a startup drive, an NVIDIA Titan X with 12 GB of Video RAM, 64 GB of 1333MHz RAM, 2 6TB internals and a 4TB internal. This is all doable for around $4000, much cheaper than a new Trashcan Macpro with the added bonus of an NVIDIA graphics card VS the unupgradeable ATI graphics cards in the new MacPro.
Honestly if I had the money this is what I would love to do with my Mac! It would give me years more life with my Mac and really make it fast!