Data Science / Particle Physics PC build with Threadripper! Thoughts?

Hello all, I am building a PC for the first time! I develop and test software and firmware for particle physics research. This requires lots of data-crunching through large files, some heavy CPU simulations, and a lot of machine learning/data science. My budget is fairly high since I have taken on a part time job (outside of research) to help pay for this build.

I have already received a free Titan Xp thanks to Nvidia's GPU academic seeding program. My budget is allocated for a build around this GPU, with space to increase to three of these GPUs in the coming year.

Requirements

Most of the leg work for my research is ran at my institutions batch CPU computing system. What I need is a local PC that compliments my institution's capabilities. This mainly means fast GPUs to develop machine learning algorithms on. What I (think) I would like from my PC is:

• Plenty of power and PCIe lanes to support 3 x Titan X in the future. Starting with one for now.
• Lots of fast memory, mostly for machine learning and opening large data files into memory (sometimes needed).
• A fast CPU that can handle the PCIe lanes for the GPUs and plenty of threads so I can turn around small, local simulations quickly.
• Large, fast HDD storage. I plan to run in RAID 5 configuration, so I want to start with 3 HDDs.
• One SSD for Linux OS (Ubuntu) + fast access data.
• One SSD for Windows OS + games.

Budget

My preferred budget is around £3500 for the build, max of £3750/$4900. The GPU is already provided, so this budget is for the rest of the machine.

I plan to add a custom liquid cooling loop next month, which is another £500 or so. For now, I want a cheap and easy aircooler for the CPU.

I already have the cash, so I am just looking for some final thoughts before I begin to order the parts!

Country of Origin

I am building this computer for the UK, but I can potentially access parts from the US.

Potential Build

PCPartPicker part list / Price breakdown by merchant

Type	Item	Price
CPU	AMD - Threadripper 1900X 3.8GHz 8-Core Processor	£448.90 @ Alza
Motherboard	Gigabyte - X399 AORUS Gaming 7 ATX TR4 Motherboard	£597.54 @ More Computers
Memory	G.Skill - Trident Z 64GB (4 x 16GB) DDR4-3200 Memory	£708.10 @ Ebuyer
Storage	Samsung - 850 EVO-Series 1TB 2.5" Solid State Drive	£275.00 @ Amazon UK
Storage	Samsung - 850 EVO-Series 1TB 2.5" Solid State Drive	£275.00 @ Amazon UK
Storage	Western Digital - Black 6TB 3.5" 7200RPM Internal Hard Drive	£228.17 @ CCL Computers
Storage	Western Digital - Black 6TB 3.5" 7200RPM Internal Hard Drive	£228.17 @ CCL Computers
Storage	Western Digital - Black 6TB 3.5" 7200RPM Internal Hard Drive	£228.17 @ CCL Computers
Case	Corsair - Air 540 ATX Mid Tower Case	£114.00 @ Aria PC
Power Supply	Corsair - AX1500i 1500W 80+ Titanium Certified Fully-Modular ATX Power Supply	£383.99 @ Ebuyer
Prices include shipping, taxes, rebates, and discounts
Total	£3487.04
Generated by PCPartPicker 2017-10-27 17:44 BST+0100

Extra Thoughts

The things I need help on are:

• Cheap air cooler recommendation. I will only use this for a month or so, the switch to liquid cooling.
• Memory compatibility for threadripper. I also want to keep the option of 128 GB in the future, so I am going for 16 GB sticks.
• HDD choice. I picked one that looked like a good balance of size/price/speed. I want to run in RAID 5, so I am starting with 3 disks.
• I plan to use this optical bay converter to fit in more 3.5 disks http://www.icydock.com/goods.php?id=157

Thanks so much for your help r/buildapc!