$1200 4k gaming pc??

Solution
Using the PCPP link from the video, because I dont count youtube as a source of information
PCPartPicker part list / Price breakdown by merchant

CPU: Intel Core i5-6600K 3.5GHz Quad-Core Processor ($219.99 @ Newegg)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler ($29.99 @ Newegg)
Motherboard: Asus Z170 PRO GAMING ATX LGA1151 Motherboard ($152.98 @ Newegg)
Memory: Kingston HyperX Fury Black 16GB (2 x 8GB) DDR4-2133 Memory ($72.99 @ SuperBiiz)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($47.49 @ OutletPC)
Video Card: Asus GeForce GTX 1080 8GB STRIX Video Card ($629.99...
Using the PCPP link from the video, because I dont count youtube as a source of information
PCPartPicker part list / Price breakdown by merchant

CPU: Intel Core i5-6600K 3.5GHz Quad-Core Processor ($219.99 @ Newegg)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler ($29.99 @ Newegg)
Motherboard: Asus Z170 PRO GAMING ATX LGA1151 Motherboard ($152.98 @ Newegg)
Memory: Kingston HyperX Fury Black 16GB (2 x 8GB) DDR4-2133 Memory ($72.99 @ SuperBiiz)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($47.49 @ OutletPC)
Video Card: Asus GeForce GTX 1080 8GB STRIX Video Card ($629.99 @ SuperBiiz)
Case: NZXT S340 (Black/Red) ATX Mid Tower Case ($64.99 @ SuperBiiz)
Power Supply: EVGA 600B 600W 80+ Bronze Certified ATX Power Supply ($44.16 @ Amazon)
Total: $1250.59
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2016-08-24 23:51 EDT-0400

Lower speed RAM, no SSD, and cheaped out on the PSU.
Overall its not a great system, but its not bad either.
 
Solution
PCPartPicker part list / Price breakdown by merchant

CPU: Intel Core i5-6500 3.2GHz Quad-Core Processor ($204.99 @ Newegg)
CPU Cooler: Deepcool GAMMAXX 400 74.3 CFM CPU Cooler ($14.99 @ Newegg)
Motherboard: Gigabyte GA-H170-D3H ATX LGA1151 Motherboard ($93.99 @ SuperBiiz)
Memory: G.Skill Ripjaws V Series 16GB (2 x 8GB) DDR4-2400 Memory ($62.99 @ Newegg)
Storage: OCZ TRION 150 240GB 2.5" Solid State Drive ($59.99 @ Amazon)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($47.49 @ OutletPC)
Video Card: Gigabyte GeForce GTX 1080 8GB G1 Gaming Video Card ($629.99 @ SuperBiiz)
Case: Zalman Z1 ATX Mid Tower Case ($24.99 @ Newegg)
Power Supply: SeaSonic S12II 520W 80+ Bronze Certified ATX Power Supply ($58.99 @ SuperBiiz)
Total: $1185.41
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2016-08-25 00:28 EDT-0400
 
Overclocking variant:
PCPartPicker part list / Price breakdown by merchant

CPU: Intel Core i5-6600K 3.5GHz Quad-Core Processor ($219.99 @ Newegg)
CPU Cooler: Deepcool GAMMAXX 400 74.3 CFM CPU Cooler ($14.99 @ Newegg)
Motherboard: Gigabyte GA-Z170-HD3 ATX LGA1151 Motherboard ($99.60 @ OutletPC)
Memory: G.Skill Ripjaws V Series 16GB (2 x 8GB) DDR4-2400 Memory ($62.99 @ Newegg)
Storage: OCZ TRION 150 240GB 2.5" Solid State Drive ($59.99 @ Amazon)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($47.49 @ OutletPC)
Video Card: Gigabyte GeForce GTX 1080 8GB G1 Gaming Video Card ($629.99 @ SuperBiiz)
Case: Zalman Z1 ATX Mid Tower Case ($24.99 @ Newegg)
Power Supply: SeaSonic S12II 520W 80+ Bronze Certified ATX Power Supply ($58.99 @ SuperBiiz)
Total: $1206.02
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2016-08-25 00:30 EDT-0400
 


@OP, the PSU is very unstable in this build, and many components can be improved.......
The poster himself recognised these shortcomings, but I listed two variants below which both perform better and are higher quality.
I'll update though and post below, prices have changed dramatically since then.
 
PCPartPicker part list / Price breakdown by merchant

CPU: Intel Core i5-6600K 3.5GHz Quad-Core Processor ($229.99 @ B&H)
CPU Cooler: Cooler Master Hyper 212 EVO 82.9 CFM Sleeve Bearing CPU Cooler ($26.88 @ OutletPC)
Motherboard: ASRock Z170 Pro4S ATX LGA1151 Motherboard ($89.99 @ Newegg)
Memory: Avexir Core Series 16GB (2 x 8GB) DDR4-2400 Memory ($74.99 @ Newegg)
Storage: Crucial MX300 275GB M.2-2280 Solid State Drive ($70.98 @ Directron)
Storage: Hitachi Deskstar 7K2000 2TB 3.5" 7200RPM Internal Hard Drive ($49.95 @ Amazon)
Video Card: Zotac GeForce GTX 1080 8GB AMP! Edition Video Card ($569.99 @ Amazon)
Case: Zalman Z1 Neo ATX Mid Tower Case ($39.99 @ Amazon)
Power Supply: SeaSonic S12II 620W 80+ Bronze Certified ATX Power Supply ($49.99 @ B&H)
Total: $1202.75
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2016-12-20 03:00 EST-0500