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Setting up A build for my brother

PCPartPicker part list / Price breakdown by merchant

CPU: Intel Core i5-7600K 3.8GHz Quad-Core Processor ($232.99 @ SuperBiiz)
CPU Cooler: CRYORIG H7 49.0 CFM CPU Cooler ($34.88 @ OutletPC)
Motherboard: ASRock Z270 Pro4 ATX LGA1151 Motherboard ($117.99 @ SuperBiiz)
Memory: G.Skill Ripjaws V Series 16GB (2 x 8GB) DDR4-2800 Memory ($89.99 @ Newegg)
Storage: ADATA Premier SP550 240GB 2.5" Solid State Drive ($69.99 @ NCIX US)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($49.33 @ OutletPC)
Video Card: MSI GeForce GTX 1060 6GB 6GB GAMING X Video Card ($269.99 @ B&H)
Case: NZXT S340 (White) ATX Mid Tower Case ($66.99 @ B&H)
Power Supply: Corsair CXM 550W 80+ Bronze Certified Semi-Modular ATX Power Supply ($59.99 @ Newegg)
Operating System: Microsoft Windows 10 Home OEM 64-bit ($88.58 @ OutletPC)
Total: $1080.72
Prices include shipping, taxes, and discounts when available

Generated by PCPartPicker 2017-01-30 18:00 EST-0500

PCPartPicker part list / Price breakdown by merchant

CPU: Intel Core i5-7600K 3.8GHz Quad-Core Processor ($232.99 @ SuperBiiz)
CPU Cooler: CRYORIG H7 49.0 CFM CPU Cooler ($34.88 @ OutletPC)
Motherboard: ASRock Z270 Pro4 ATX LGA1151 Motherboard ($117.99 @ SuperBiiz)
Memory: G.Skill Ripjaws V Series 8GB (2 x 4GB) DDR4-2400 Memory ($53.99 @ Newegg)
Storage: ADATA Premier SP550 240GB 2.5" Solid State Drive ($69.99 @ NCIX US)
Video Card: Asus Radeon RX 480 4GB Dual Video Card ($189.99 @ Newegg)
Case: NZXT S340 (White) ATX Mid Tower Case ($62.99 @ NCIX US)
Power Supply: Corsair CXM 550W 80+ Bronze Certified Semi-Modular ATX Power Supply ($59.99 @ Newegg)
Operating System: Microsoft Windows 10 Home OEM 64-bit ($88.58 @ OutletPC)
Total: $911.39
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2017-01-30 18:02 EST-0500

imho i would go with this build.
 
Solution
Your brother will be very disappointed when he finds out that the B250 motherboard is not capable of overclocking a "K"
You want a Z270 motherboard.

A GTX1060 needs about 450w, the evga unit will work, but it is not one of their best.
Here is a quality list:
http://www.tomshardware.com/forum/id-2547993/psu-tier-list.html

I might suggest Seasonic which is always good.
Here is a tier 2 S12II 520 Bronze 520W for less.
https://www.newegg.com/Product/Product.aspx?Item=N82E16817151094
Do not worry about modular, your case will hide the few extra leads.