Admiral Koba

Now, that's a very neat idea. Beautiful design with a balling machine to go with it. I'm interested to see how this project turns out.

If you haven't bought the machine yet (my assumption) - perhaps (as you've gone with a 144 Hz monitor) you might want to spend the extra $80 to go up to a GTX 1060 6GB rather than an extra stick of RAM (however some modern games do appreciate the extra RAM over the graphics horsepower)

Your connection doesn't change, you are just pushing all the data you would normally push direct through a tunnel towards another server. Your ISP will just see it as connecting to another device on the internet.

It's not the same. Powerline adapters uses your house's electrical wiring. If your house is old then the electrical wiring can have an affect on the powerline. Pricing won't matter. Any device you get will yield the same results.

According to the manufacturer of your gateway - to port forward those are the steps you need to follow. Putting in your exact IP may not work correctly.

PCPartPicker part list / Price breakdown by merchant Type Item Price CPU AMD - Ryzen 5 2600 3.4 GHz 6-Core Processor $154.99 @ Amazon Motherboard Gigabyte - B450 AORUS PRO WIFI (rev. 1.0) ATX AM4 Motherboard $123.98 @ Newegg Memory Corsair - Vengeance LPX 16 GB (2 x 8 GB) DDR4-3000 Memory $119.99 @ Amazon Storage Kingston - A400 240 GB 2.5" Solid State Drive $36.99 @ Newegg Business Storage Western Digital - Caviar Blue 1 TB 3.5" 7200RPM Internal Hard Drive $44.89 @ OutletPC Video Card Asus - GeForce GTX 1070 8 GB Dual Series Video Card $304.99 @ Newegg Case Corsair - Carbide Series 275R (Black w/Tempered Glass) ATX Mid Tower Case $64.99 @ Amazon Power Supply EVGA - SuperNOVA G3 650 W 80+ Gold Certified Fully-Modular ATX Power Supply $79.89 @ OutletPC   Prices include shipping, taxes, rebates, and discounts     Total (before mail-in rebates) $950.71   Mail-in rebates -$20.00   Total $930.71   Generated by PCPartPicker 2018-12-28 06:44 EST-0500   Would probably be my rough estimate for a system like this. Good luck in your search.
 

AMD Ryzen 5 2600
MSI- B450-A pro Atx motherboard
G-Skill 2x8GB DDR4 2800Mhz
SSD 240gb And 1TB HDD
AMD RX 570 8GB GPU
550W Power Supply

I'd probably reccomend the Asus RT-AC68U - it's at the higher end of your budget but has a decent range from what I've heard and supports AiMesh (seen here) so could allow you to extend further down the line with more APs. It's fairly decent in NewEgg right now.
 
That being said, a Netgear Nighthawk AC1900/AC2300 also fits within your budget and is a solid choice too. Good luck in your search.

The cables are flat, flat patch cables aren't the rarest thing in the world. They seem just like standard STP (shielded twisted pair) cables to me. (most CAT6 is 32 AWG however - so wire is a little thicker)

It's not a blanking plate, it's a shelf. Look under it on the first image to give you a better view at it.
 
https://www.reichelt.com/gb/en/19-rack-housing-2-u-sin-2-he-sw-p247241.html?ARTICLE=247241&&r=1 - is very similar if you're interested.

Likely to not have come with the rack.

For the cost of one of those boxes I could get a few spools of CAT6 cable, hundreds of RJ45 connectors, new crimpers, AND hire somebody off Craigslist to do the work for a bunch of cabinets while still having money left over for a bunch of shiny new UniFi APs for all the wireless I won't need.

The APU is fine, you can just opt out of using the integrated graphics by putting your video cable into the graphics card (which you would do anyway)

You don't need it. It's safe (made by LogMeIn - makers of LastPass etc.) but there are more elegant ways of doing it - nice way to play if you don't want to port forward however.

Free shipping in the contiguous US & Canada. OP asked for price in $ so assumption is that they're in North America. You raise a valid point however.

G.Skill RIPJAWS KM570 have RGB MX Blues on Amazon for ~$100. The keyboard has media keys and has the G.Skill Driver System for customization through software.