Is this build okay? Can someone fix this if it isn't?

Solution
If you are building it for a friend. Odds are that friend won't mess around with overclocking. But if they do this build will save money and allow some OC. Based on current prices. The Core i7-6700K offers the best price to performance ratio for an i7. Given it's 4.0Ghz and can be overclocked, even without OC it is a better deal currently. This build will have hardly any difference in gaming performance for a much more reasonable price.

PCPartPicker part list / Price breakdown by merchant

CPU: Intel Core i7-6700K 4.0GHz Quad-Core Processor ($277.22 @ Amazon)
CPU Cooler: be quiet! PURE ROCK 51.7 CFM Sleeve Bearing CPU Cooler ($27.98 @ NCIX US)
Motherboard: MSI Z170M Mortar Micro ATX...
I'd recommend the follow changes:

get a motherboard with the proper chipset, Z270
Upgrade the GPU to a RX 580 8gb

The motherboard in there is a Z170 and while it can support a Kaby lake CPU, it might need a BIOS update first and that can be a PITA without a functioning CPU in it.
The RX 580 has shown itself to be the better card over the 1060 and for the same price, possibly less.

For whether or not the CPU is appropriate, it depends on what they want to use it for. If gaming and streaming, the 7700k or AMD 1700X are a good choice. the extra threads will help. For straight up gaming, the 7600k is good for now, but if the intention is to have the system a while (over a year) the 7700k is a good idea.
 

Supahos

Expert
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PCPartPicker part list / Price breakdown by merchant

CPU: AMD Ryzen 5 1600 3.2GHz 6-Core Processor ($218.98 @ NCIX US)
CPU Cooler: CRYORIG H7 49.0 CFM CPU Cooler ($34.89 @ OutletPC)
Motherboard: MSI B350 PC MATE ATX AM4 Motherboard ($98.99 @ SuperBiiz)
Memory: Corsair Vengeance LPX 16GB (2 x 8GB) DDR4-3000 Memory ($122.99 @ Best Buy)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($48.88 @ OutletPC)
Video Card: Gigabyte GeForce GTX 1060 6GB 6GB WINDFORCE OC 6G Video Card (Purchased For $0.00)
Case: Corsair Air 540 ATX Mid Tower Case ($109.99 @ Newegg)
Power Supply: EVGA SuperNOVA G2 850W 80+ Gold Certified Fully-Modular ATX Power Supply ($105.57 @ Amazon)
Operating System: Microsoft Windows 10 Home OEM 64-bit ($88.58 @ OutletPC)
Case Fan: Corsair Air Series AF140 Quiet Edition 67.8 CFM 140mm Fan ($17.88 @ OutletPC)
Total: $846.75
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2017-04-25 23:13 EDT-0400

Nothing inherently wrong with that build but this is a better match for a 1060
 
added solid state drive and tweaked the rest, no additional fans needed for the case i picked. Kept costs down. No need to spend big with a 1060.

PCPartPicker part list / Price breakdown by merchant

CPU: AMD Ryzen 5 1600 3.2GHz 6-Core Processor ($218.98 @ NCIX US)
CPU Cooler: CRYORIG H7 49.0 CFM CPU Cooler ($34.89 @ OutletPC)
Motherboard: ASRock AB350 Pro4 ATX AM4 Motherboard ($88.98 @ Newegg)
Memory: G.Skill Ripjaws V Series 16GB (2 x 8GB) DDR4-2800 Memory ($111.79 @ OutletPC)
Storage: Samsung 850 EVO-Series 250GB 2.5" Solid State Drive ($107.99 @ B&H)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($48.88 @ OutletPC)
Video Card: Gigabyte GeForce GTX 1060 6GB 6GB WINDFORCE OC 6G Video Card ($0.00)
Case: Phanteks Enthoo Pro M ATX Mid Tower Case ($59.99 @ Newegg)
Power Supply: EVGA SuperNOVA GS 550W 80+ Gold Certified Fully-Modular ATX Power Supply ($76.98 @ Newegg)
Operating System: Microsoft Windows 10 Home OEM 64-bit ($88.58 @ OutletPC)
Total: $837.06
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2017-04-25 23:21 EDT-0400
 
If you are building it for a friend. Odds are that friend won't mess around with overclocking. But if they do this build will save money and allow some OC. Based on current prices. The Core i7-6700K offers the best price to performance ratio for an i7. Given it's 4.0Ghz and can be overclocked, even without OC it is a better deal currently. This build will have hardly any difference in gaming performance for a much more reasonable price.

PCPartPicker part list / Price breakdown by merchant

CPU: Intel Core i7-6700K 4.0GHz Quad-Core Processor ($277.22 @ Amazon)
CPU Cooler: be quiet! PURE ROCK 51.7 CFM Sleeve Bearing CPU Cooler ($27.98 @ NCIX US)
Motherboard: MSI Z170M Mortar Micro ATX LGA1151 Motherboard ($91.99 @ SuperBiiz)
Memory: Team Dark 16GB (2 x 8GB) DDR4-2400 Memory ($107.99 @ Newegg)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($48.88 @ OutletPC)
Video Card: Gigabyte GeForce GTX 1060 6GB 6GB WINDFORCE OC 6G Video Card (Purchased For $0.00)
Case: Phanteks ECLIPSE P400 ATX Mid Tower Case ($69.99 @ Amazon)
Power Supply: SeaSonic 650W 80+ Gold Certified Semi-Modular ATX Power Supply ($76.99 @ SuperBiiz)
Operating System: Microsoft Windows 10 Home OEM 64-bit ($89.98 @ NCIX US)
Total: $791.02
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2017-04-25 23:22 EDT-0400

Heck, if the budget is $1,000. There is now room for a large SSD. It'll be far more noticeably than a minor clock boost. The SSD makes a huge difference in everyday use. Games and levels load much faster. I would never go back to a hard drive.

PCPartPicker part list / Price breakdown by merchant

CPU: Intel Core i7-6700K 4.0GHz Quad-Core Processor ($277.22 @ Amazon)
CPU Cooler: be quiet! PURE ROCK 51.7 CFM Sleeve Bearing CPU Cooler ($27.98 @ NCIX US)
Motherboard: MSI Z170M Mortar Micro ATX LGA1151 Motherboard ($91.99 @ SuperBiiz)
Memory: Team Dark 16GB (2 x 8GB) DDR4-2400 Memory ($107.99 @ Newegg)
Storage: OCZ TRION 150 960GB 2.5" Solid State Drive ($236.49 @ Amazon)
Video Card: Gigabyte GeForce GTX 1060 6GB 6GB WINDFORCE OC 6G Video Card (Purchased For $0.00)
Case: Phanteks ECLIPSE P400 ATX Mid Tower Case ($69.99 @ Amazon)
Power Supply: SeaSonic 650W 80+ Gold Certified Semi-Modular ATX Power Supply ($76.99 @ SuperBiiz)
Operating System: Microsoft Windows 10 Home OEM 64-bit ($89.98 @ NCIX US)
Total: $978.63
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2017-04-25 23:25 EDT-0400
 
Solution
7700 serries CPU is likely to be incompatable with a z170 motherboard. 100 serries borads need a bios update to support 7xxx serries kaby lake CPUs and at his point it is still luck of the draw if you get one with supported bios (and you cant update the bios with a non-supported CPU).

850w is overkill for a single card, and frankly SLI is not worth the cost vs just buying a single stronger GPU so you dont need any more then 550w for non-overclock, 650w for overclock.