Added to the 2013 Mac Pro coverage is a new section on transitioning the existing 12-core Mac Pro with all its SSDs and hard drives to the 2013 Mac Pro.
A transition overview is followed by 5 problem-solving pages. Total cost for hardware to compensate for the lack of no internal expansion approaches $2000 in my case.
My system is a little more expansive than most. It poses additional transition challenges to get two PCIe SSDs, three 6G SSDs, one 3G SSD and two 4TB hard drives—all internal now—connected to the new Mac Pro.