An update to this old thread as I am planning on going down this path shortly. I found two decent stores Zcomputers and TheServerStore in the USA that focus on Workstations - the HP Z820 in particular which seems a very decent beast. I am tossing up two configurations:
HP Z820 Workstation USD $1,824
Processors: 2x Xeon® E5-2695 v2 2.4GHz Twelve Core Processors, (24C/48T) - $760.00
Memory: 64GB (8x 8GB) DDR3 Memory - $160.00
Primary Hard Drive: 400GB SSD - $180.00
Second Hard Drive: No Hard Drive
Third Hard Drive: No Hard Drive
Fourth Hard Drive: No Hard Drive
Video Card: NVIDIA GeForce GTX 680 XLR8 - $160.00
Optical Drive: DVD-RW
Workstation PCIe Expansion: None Installed
Operating System: Windows 10 Professional 64-bit Installed - $45.00
or
HP Z820 Workstation USD $1,604
Processors: 2x Xeon® E5-2690 v2 3.0GHz Ten Core Processors, (20C/40T) - $700.00
Memory: 64GB (8x 8GB) DDR3 Memory - $160.00
Primary Hard Drive: 400GB SSD - $180.00
Second Hard Drive: No Hard Drive
Third Hard Drive: No Hard Drive
Fourth Hard Drive: No Hard Drive
Video Card: AMD Radeon HD 8350
Optical Drive: DVD-RW
Workstation PCIe Expansion: None Installed
Operating System: Windows 10 Professional 64-bit Installed - $45.00
The dual 10 core 3.0 GHZ Xeons would probably run poorly mutli threaded applications (like games) better because of its 25% higher clock speed across all threads. So its a trade off between 20 vs 24 physical cores.
The supplier also confirmed it can run a single NVidia GTX 1070 or 1080 (not SLI because only Workstation cards - think NVidia Quadro cards have that enabled).
One thing I wasn't aware of is dual cpu machines take about two minutes from power on to the normal BIOS boot sequence appearing on the screen. Apparently they go thru a prorietary hardware okay check and nothing much appears on the screen until that is finished!
So from the lasy post in February - those 12 core CPUs at 2.4GHz are available for about USD $760 the pair!