With that kind of money and without any preferences, here's my entry:
GODLIKE RGB GAMING
PCPartPicker part list /
Price breakdown by merchant
CPU: Intel - Core i7-8700K 3.7GHz 6-Core Processor ($378.79 @ SuperBiiz)
CPU Cooler: Corsair - H150i PRO 47.3 CFM Liquid CPU Cooler ($169.99 @ Amazon)
Motherboard: MSI - Z370 GODLIKE GAMING EATX LGA1151 Motherboard ($499.99 @ Amazon)
Memory: Corsair - Vengeance RGB 32GB (4 x 8GB) DDR4-3000 Memory ($424.73 @ Amazon)
Storage: Samsung - 960 EVO 1TB M.2-2280 Solid State Drive ($448.99 @ SuperBiiz)
Storage: Samsung - 960 EVO 1TB M.2-2280 Solid State Drive ($448.99 @ SuperBiiz)
Storage: Samsung - 960 EVO 1TB M.2-2280 Solid State Drive ($448.99 @ SuperBiiz)
Video Card: Asus - GeForce GTX 1080 Ti 11GB STRIX GAMING Video Card ($1190.89 @ OutletPC)
Case: Corsair - 780T ATX Full Tower Case ($162.86 @ Amazon)
Power Supply: SeaSonic - PRIME Titanium 750W 80+ Titanium Certified Fully-Modular ATX Power Supply ($179.99 @ B&H)
Operating System: Microsoft - Windows 10 Home OEM 64-bit ($92.99 @ Best Buy)
Case Fan: Corsair - LL120RGB LED (Three Fans With Lighting Node PRO) 43.2 CFM 120mm Fans ($119.99 @ Amazon)
Case Fan: Corsair - LL140 RGB LED 51.5 CFM 140mm Fan ($39.99 @ Amazon)
Case Fan: Corsair - LL140 RGB LED (TwoFans With Lighting Node PRO) 51.5 CFM 140mm Fans ($99.99 @ Amazon)
Keyboard: Corsair - STRAFE RGB Wired Gaming Keyboard ($132.95 @ Amazon)
Mouse: Corsair - Sabre RGB Wired Optical Mouse ($38.99 @ Newegg)
Headphones: Corsair - VOID PRO RGB (Black) 7.1 Channel Headset ($99.95 @ Amazon)
Total: $4979.06
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2018-01-28 10:25 EST-0500
Few words
Intel's 8th gen K-series Core i7 as a CPU, picked the best/biggest Corsair AIO to cool it. You can mount the 360mm rad as top exhaust or front intake,
specs:
http://www.corsair.com/en-us/hydro-series-h150i-pro-rgb-360mm-liquid-cpu-cooler
With the budget of yours, i picked the best MoBo from MSI which has plethora of features, including lots of RGB LEDs,
specs:
https://www.msi.com/Motherboard/Z370-GODLIKE-GAMING
To match the MoBo RGB LEDs, put in 32GB of Corsair Vengeance RGB 3000 Mhz RAM which is more than enough for any tasks you throw at it,
specs:
http://www.corsair.com/en-us/vengeance-rgb-32gb-4-x-8gb-ddr4-dram-3000mhz-c15-memory-kit-cmr32gx4m4c3000c15
At this price point, forget slow HDDs and SATA SSDs. To store all your data, i put in 3x 1TB Samsung 960 Evo M.2 NVMe SSDs, making the total storage space 3TB. All 3x NMVe SSDs mount directly to your MoBo to keep the build's look pristine,
specs: https://www.samsung.com/us/computing/memory-storage/solid-state-drives/ssd-960-evo-m-2-1tb-mz-v6e1t0bw/
For GPU, went with Asus GTX 1080 Ti STRIX GAMING which is the best GPU to be used for 4K,
specs: https://www.asus.com/Graphics-Cards/ROG-STRIX-GTX1080TI-11G-GAMING/
To see from afar that you got plenty for your money, i picked an ATX full-tower case for your build. Corsair 780T is big enough case to fit all your hardware while providing a premium look,
specs:
http://www.corsair.com/en-gb/graphite-series-780t-full-tower-pc-case
Only the best PSU money can buy at current date deserves to power all that hardware, so put it Seasonic PRIME 750 80+ Titanium PSU,
specs:
https://seasonic.com/prime-titanium
review:
http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story&reid=481
(My Skylake build is also powered by PRIME 80+ Titanium PSU but mine is 650w, full specs with pics in my sig.)
To complete the RGB LED look of the build, i included 3x Corsair LL120 and 3x Corsair LL140 fans. 120mm fans are for replacing stock fans on the rad while 140mm fans are for replacing the case's stock fans,
specs:
http://www.corsair.com/en-us/cooling/ll-series-fans
video review:
https://www.youtube.com/watch?v=KZ8acay59cY
I also added Corsair mechanical RGB KB, Corsair RGB mouse and Corsair RGB headset that you can sync with Corsair LL-series fans and Corsair AIO to complete the RGB setup of your PC.
KB specs:
http://www.corsair.com/en-eu/strafe-rgb-mechanical-gaming-keyboard-cherry-mx-silent-eu
mouse specs:
http://www.corsair.com/en-eu/sabre-rgb-gaming-mouse
headset specs:
http://www.corsair.com/en-eu/void-pro-rgb-usb-premium-gaming-headset-with-dolby-headphone-7-1-carbon-eu
Note: PC case, KB, mouse and headset are personal choices and feel free to replace them with the ones you like the most.
(I also have Corsair Strafe RGB, Corsair Sabre RGB and Corsair Void Pro RGB in use with my Skylake build.)