How does this look? What else do I need?
RAID is a way of combining two or more drives into one. There are many different types of RAID, the most common ones are RAID0 and RAID1. RAID0 basically "stripes" the data across the two drives, so you get doubled the capacity of one drive and theoretically double the performance (though it's not always that simple). However, if one drive fails, you lose all your data, so you're essentially twice as likely to lose your data (two fail points vs. 1). RAID1, on the other hand, mirrors the data between the two drives. It doesn't double the capacity, but it also theoretically doubles the performance and in this case, you need both drives to fail to lose your data, basically it makes it more likely for your data not to be lost. I don't recommend RAID0 since for SSDs unless you're doing professional stuff it doesn't give much of a performance jump and it makes you more likely to have drives fail. RAID1 you could do if you're really paranoid though unless you're keeping extremely sensitive info I don't recommend it either.
I made a few small changes, including swapping out the two 500gb SSDs for one 1 TB SSD (it's $35 cheaper), switching the psu for a cheaper yet better one, getting windows from Kinguin.net instead (I know it looks shady but it works, I would get the buyer protection thing just in case but there shouldn't be any issues, I've had friends use it no problem. If you really don't like it though you could get a $100 copy that is definitely legit but this should be fine), and removing the sound card (you shouldn't need it unless you have really good headphones).
Also, do you really need a cd card reader? The kinguin thing only comes with a code, not a cd, and you can get a Windows installation cd from Microsoft for free (assuming you have a flash drive with at least 5gb capacity). Idk if you have other uses for it.
And just make sure to get an aftermarket cooled 1080 ti. They should be out in a week or two.
Anyhow, here's the list:
PCPartPicker part list / Price breakdown by merchant
CPU: Intel Core i7-7700K 4.2GHz Quad-Core Processor ($449.95 @ Vuugo)
CPU Cooler: Corsair H100i v2 70.7 CFM Liquid CPU Cooler ($124.99 @ Amazon Canada)
Motherboard: Asus STRIX Z270-E GAMING ATX LGA1151 Motherboard ($257.99 @ PC Canada)
Memory: G.Skill Ripjaws V Series 16GB (2 x 8GB) DDR4-3200 Memory ($158.98 @ DirectCanada)
Storage: Samsung 850 EVO-Series 1TB 2.5" Solid State Drive ($419.98 @ DirectCanada)
Storage: Seagate Barracuda 2TB 3.5" 7200RPM Internal Hard Drive ($86.74 @ Vuugo)
Video Card: EVGA GeForce GTX 1080 Ti 11GB Founder Edition Video Card ($979.99 @ Amazon Canada)
Case: Fractal Design Define R5 (Titanium) ATX Mid Tower Case ($139.99 @ Newegg Canada)
Power Supply: EVGA SuperNOVA G2 650W 80+ Gold Certified Fully-Modular ATX Power Supply ($104.99 @ NCIX)
Optical Drive: Asus DRW-24B1ST/BLK/B/AS DVD/CD Writer ($24.75 @ Vuugo)
Case Fan: Corsair Air Series AF140 Quiet Edition 67.8 CFM 140mm Fan ($22.99 @ Amazon Canada)
Other: NZXT APERTURE M 5.25 Bay Multi-Media Mesh Style Card Reader w. Dual ($44.99 @ Memory Express)
Other: Windows 10 Home ($38.39)
Total: $2854.72
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2017-03-26 09:34 EDT-0400
As for cable management, I personally just like to use Velcro straps and zip ties. Unless you want cable combs to really make it looks nice (though those cost quite a bit), zip ties and Velcro straps should suffice. You could get something like this, and just tell the guy building it:
Use the Velcro straps to keep cables neat.
I assume they've built pcs before so it shouldn't need too much instruction 