A new build

Mesh
Thanks Darin, good point on the PSU. I'm a little concerned on the CPU cooler as well.....would that Phanteks be enough for his gaming? (he may or may not do a little OCing....he's going to decide on that out later). Any recommendations would be greatly appreciated (I know my NH-D14 is excellent, but it's also huge and his case may not be big enough). 
Also, not sure how good those SSD and HD drives are... 

Hard drives seem to be really hit and miss lately according to reviews I've read. Especially the less expensive ones. I have several Western Digital Black series hard drives that have been great the last couple of years (3x 3TB and a couple 1 TB models). I use one of these for my samples in my music PC. The others are used for video editing workstations (my real job). However, I've noticed people having some issues with the newer 4TB and up models. Mainly 'clicking' noises and such. Western Digital has just released the 'Gold' series, which are touted to be faster than the Black series, and very reliable. I just ordered a 1TB model to try out. The Black series and Gold series are both on the higher-end, expensive drives though. Of the lower-end drives, I've had good luck with Western Digital also, but they seem to be having some QC issues of late. Just be sure you get at least a 7200 RPM drive. I would read reviews on NewEgg before deciding on one.
 
As for SSD drive.. Samsung is considered king. I've not tried any other brand, but others may be just fine. Again, best bet is to read reviews.
 
Just some food for thought: I just built this system (literally last weekend) for my new video editing system:
 
Processor:
Intel Core i7-7700K Kaby Lake Quad-Core 4.2 GHz LGA 1151 91W BX80677I77700K Desktop Processor
 
Motherboard:
GIGABYTE GA-Z270-Gaming K3
 
Memory:
CORSAIR Dominator Platinum 32GB (4 x 8GB) 288-Pin DDR4 SDRAM DDR4 3000 (PC4 24000) Desktop Memory Model CMD32GX4M4C3000C15
 
System Drive:
SAMSUNG 850 EVO 2.5" 500GB SATA III 3-D Vertical Internal Solid State Drive (SSD) MZ-75E500B/AM
 
Case:
Phanteks Enthoo Luxe PH-ES614LTG_BK Black Aluminum Faceplates Tempered Glass Panel Steel Chassis ATX Full Tower Computer Case with RGB Illumination
 
Power:
Seasonic Flagship PRIME SERIES SSR-1000GD 1000W GOLD FULL MODULAR ATX12V & EPS12V 135mm FDB Fan Super Quiet Power Supply
 
Video:
EVGA GeForce GTX 1060 SC GAMING, ACX 2.0 (Single Fan), 06G-P4-6163-KR, 6GB GDDR5, DX12 OSD Support (PXOC), Only 6.8 Inches
 
Windows 10 Pro
 
I also added in some other stuff of little relevance to anyone but myself. I spent about $2000 total.
 
The system was a breeze to set up, and very fast.. Did I say FAST? Lol. The trouble I ran into was with the heat-sink/fan that I purchased. The 7700k runs pretty hot. The stock K-Series Intel heat-sink/fan I ordered just doesn't cut it. The CPU was getting close to 100 degrees celsius under load. FAR too hot. So I've ordered a Noctua NH-D15 to hopefully solve the problem. The full-tower case I have should accommodate it.
 
Other than the above problem, this system has been very stable in the little time that I've had it. Adobe Premiere, After Effects and Photoshop are a pleasure to work.
 
Your nephew will probably want the bigger video card that you have already picked out. That thing looks like a beast! I've had great luck with both Gigabyte and EVGA video cards.
 
As for the memory, he doesn't really need the 32GB that I used. There is a 16GB kit of that RAM available that would probably be plenty enough for a gaming rig. If he does decide to start doing video editing and graphics etc., he would very much appreciate the 32GB.
 
I purchased all of these parts from NewEgg.com.
 
Edit:
I forgot to mention that the 1000 watt power supply is complete overkill, even for me. Lol. Also, if he wants to stick with a mid tower case, Jack's suggestion on a water cooling solution is certainly something to consider.
 

They use graphics cards to "mine" Bitcoin (and alternatives). There was a time where you could make serious money with an affordable system. I think it's getting pretty hard now as the required computer power is pretty large compared to how many coins you will actually mine.

I buy most (practically all) of my PC parts either from newegg or Amazon.  Amazon has much better return policy than newegg (a negative about newegg).  I've never purchased anything from Outlet PC so I don't know how they are.
 
When I built my last desktop DAW system, I got the motherboard, CPU, power supply and cooler from Amazon.  The BeQuiet case and Corsair memory from newegg.  I reused a Samsung EVO 850 (500GB) SSD and 2TB hard drive, Monitor, and wireless Keyboard and Mouse from my old DAW desktop.  I'm not using a separate video card.