Overall a very good and powerful build. I would just look at the motherboard as a better mid range motherboard would better suit the 9700K especially with a better VRM setup than the ASUS TUF...
The Gigabyte Aorus Elite at $172.04 has a 12 Phase setup but also the MSI Gaming Edge or the ASRock Extreme4 which may be even cheaper than the TUF and still has a better VRM setup will also be worth a look.
I have also changed the Power Supply to the Seasonic Focus Plus Gold 850w which is one of the very best power supplies you can get at the moment and is rated very highly by all..It is also fully modular...
I have included a Gigabyte RTX 2070 from Gigabyte the OC version as it is better overall in terms of performance than the Vega64 and the price is just about the same.
also the build below is slighter cheaper than your original build...
PCPartPicker part list:
https://pcpartpicker.com/list/DB4RMZ
Price breakdown by merchant: https://pcpartpicker.com/list/DB4RMZ/by_merchant/
CPU: Intel - Core i7-9700K 3.6GHz 8-Core Processor ($419.99 @ B&H)
CPU Cooler: Deepcool - CAPTAIN 240 EX 153.0 CFM Liquid CPU Cooler ($63.83 @ OutletPC)
Thermal Compound: Cooler Master - MasterGel Maker 4g Thermal Paste ($9.87 @ OutletPC)
Motherboard: Gigabyte - Z390 AORUS ELITE ATX LGA1151 Motherboard ($172.04 @ Amazon)
Memory: G.Skill - Ripjaws V Series 16GB (2 x 8GB) DDR4-3000 Memory ($119.99 @ Newegg)
Storage: Samsung - 860 Evo 1TB 2.5" Solid State Drive ($162.99 @ Amazon)
Storage: Seagate - Barracuda 3TB 3.5" 7200RPM Internal Hard Drive ($79.88 @ Amazon)
Video Card: Gigabyte - GeForce RTX 2070 8GB GAMING OC Video Card ($549.99 @ Amazon)
Case: Cooler Master - MasterBox 5t ATX Mid Tower Case ($107.51 @ Amazon)
Power Supply: SeaSonic - FOCUS Plus Gold 850W 80+ Gold Certified Fully-Modular ATX Power Supply ($74.61 @ Newegg)
Operating System: Microsoft - Windows 10 Pro OEM 64-bit ($124.79 @ OutletPC)
Sound Card: Asus - STRIX RAID DLX 24-bit 192 KHz Sound Card ($201.16 @ Walmart)
Case Fan: Cooler Master - SickleFlow (Red) 69.7 CFM 120mm Fan ($6.19 @ Monoprice)
Case Fan: Cooler Master - SickleFlow (Red) 69.7 CFM 120mm Fan ($6.19 @ Monoprice)
Case Fan: Cooler Master - SickleFlow (Red) 69.7 CFM 120mm Fan ($6.19 @ Monoprice)
Total: $2105.22
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2018-11-04 17:41 EST-0500
Dropping down to the 8700K will also save you around $60 and will provide you near on the same performance as the 9700K...If money on the CPU is not an issue then go the 9700K....