Well I haven't had time to analyze things, but late breaking facts:
Intel SSD 750 vs Samsung. The new Samsung M.2 will be x4 PCI Express with NVMe, they give a real run for the money for the Intel PCIe Express slot cards. I love the idea of a 2400MBps read with 70K IOPs and very low latency and this will be a real dog fight. The thing is that this requires a full PCI Express 3.0 with 4 lanes (x4). So it puts pressure on the overall system and probably means the Haswell-E which are really the server Xeon chips get pretty interesting.
So ideally if you want to take full advantage of a couple of these bad boys and also have a dual SLI graphics card, then you need more PCI Express lanes. The vanilla Haswell or Broadwell (14nm shrink of Haswell) has 16 PCI Express 3.0 lanes (1GBps) and 8 PCI Express 2.0 lanes (500MBps). So at a minimum you would need 8x2 or 16x for the graphics cards and 4x3 for a pair of the SSds which is a total of 28 PCI Express 3.0 lanes. The system needs several lanes for itself and that pushes you into either the lower end Haswell-E. The lowest end Haswell-E has 28 PCI Express 3.0 lanes while 40 lanes is standard.
All of three of the Haswell-E share the same LGA 2011-3 as the Xeon server family v3 (vs the 1150 of the Haswell and Broadwell) and are basically server chips. They have lower clocks but more cores and more lanes but are all overclockable. So if you were putting together a really workstation class machine here is what you would need:

• Processor. The sweet spot if you can call it that is the middle child the Intel i7-5930K which has 40 lanes and 3.5GHz clock and six cores at $600. The smaller brother the i7-5920K has 28 lanes (so still enough for either 3-way SLI 8x3=24 or 2-way SLI plus 3 PCI Express x4 SSDs) but at$450 running at 3.3GHz is probably the value leader with the extra lanes enough for most uses. So get the i7-5920K as the value leader for most uses.

• Disks I'm assuming you will want a separate boot/program SSD, another one for data storage and then a scratch SSD so that for content creation, you are getting essentially a system disk, application disk and scratch disk. That implies a minimum of three drives and 4x lanes each to 12x lanes. So you might end up with 512GB system, 1TB data and 512TB of scratch. 2TB of all SSD should make anyone happy 🙂

• Graphics. It sure looks like the sweet spot is the SLI of two cards so 2 x GTX 970 is very cost effective. Benchmarks show you need 8x lanes for each, so that's 2x8=16 lanes

• Memory. For graphics and photography and photoshop slnging around 500MB TIFFs and 4K video, you are going to need alot of memory. With the DDR4 systems, that's not a problem compared with the 32GB maximum of Haswell/Broadwell's DDR3 implementations. So call it 4-8 slots depending on where you want to end up. Perhaps 64-128GB would make anyone happy.

• http://www.tomshardware.com/reviews/intel-x99-haswell-e-overclocking,3934.html#mce_temp_url#. The motherboard is mainly about what you want to connect and the making sure you have enough slots. This means a big motherboard since you will need double width slots for the GPUs or 4 slot equivalents plus your SSDs need to either use the new small form factor connector M.2 or SFF or have their own PCI Express x4 card slots. A board like the budget MSI X99S SLI Plus is a good example at \$200, it has 8 memory slots (not the usual 4, so 64GB is easy to build) then it has 4 PCI Express slots. The first two are double width so work with two graphics cards (8x2 = 16 lanes), then you have room for the M.2 slot with 4 lanes and then two more PCI Express for NVMe memory so you use 2x8+4+2x4 = 28 lanes of PCI Express 3.0 so just right for the i57-5920K.