Welp... I was gonna get one of those newfangled Mac Pros, but after having some second thoughts, I think I've decided to build my first custom PC instead.
Wow, that is a beastly setup you got there. Though I don't think you need that much RAM - 8 or 16 is just fine. I'd also suggest an aftermarket cooler for the CPU. An air design is great but a water design is even better.
I'd recommend preparing your rig on this site, if you don't know what PCPartPicker is.
Just curious, but what are you planning to do with this computer? The setup you're going for is a lot of money, obviously
3D rendering is probably the main reason why I want a computer this powerful, and it's also the reason I decided not to go with the Mac Pro since its AMD cards don't do nearly as much for me as a couple NVIDIA cards would do for me in Blender.
Of course, there will also be the occasional game or two...
I see. Then you'll probably gonna need the 32 Gig RAM. Nvidia's a good choice here since most programs out there use CUDA tech. Other than that I think it's a pretty good rig. I'd also look at Nivida's Quadro series cards and Intel's Extreme series, but what you're going for is enough.
Processors (HEDT to be precise) that use the LGA 2011 socket have a quad channel memory controller = 8 DIMM slots = a max of 64gb of RAM supported. Regardless of what motherboard used (sporting a X79 chipset with a LGA 2011 socket), it will be supported. Well, certain form factors will warrant the # of DIMM slots available because of space requirements.
With CUDA acceleration, I can't wait to see your renders. You'll be able to up the samples and "still" get lower rendering times. It'll feel good having the ability to test a light setup without having to wait a "long" while for a scene to render.