Plumpo

I really like the idea of a rack mounted build, but only if the only requirement is that it must be rack mountable. I want to see them try and DIY a rail system with the possibility of that failing. 

If you're downloading from old/slow servers than you're going to be bottle necked by their infrastructure not yours. What happens when you try and download something off a new site like Steam/Battle.net ect? 
 
Have you done a speed test yet? http://www.speedtest.net/ to see at least a base of what your hardware and your ISP can deliver. 

https://www.guru3d.com/articles-pages/gigabyte-geforce-rtx-2080-ti-gaming-oc-11g-review,5.html

https://wccftech.com/review/gigabyte-geforce-rtx-2080-ti-gaming-oc-graphics-card-review/4/
 
looks pretty 'reference' tbh

Getting a bigger better single GPU is going to give you more consistent benefits than an SLI system. 
 
Purely anecdotal, but everyone I have known to run SLI has told me they hardly ever get to use it because of poor or complete lack of support in the games they play. 

Noctua air coolers are amazing. Not only do they work well, but they are among the easiest to install/remove. That alone is worth the higher cost for me. 

You're probably going to run into issues upgrading the PSU on a system like that unless you get another one from Dell. A lot of the time builds like this get proprietary connectors for the Motherboard and PSU so finding replacements is difficult.
 
If you already have to supply the CPU.RAM and SSD, PSU and a GPU might as well just get a cheap case and a used z87/z97 board (or one of the H variants) and skip the headache of trying to hunt down compatible OEM parts. 

Moved a completely functional machine about 300 feet in the office today. Once it got to its new home it started taking a solid 5-6 minutes to post. Once it would, another 3-4 minutes for windows to load. Then we're back in business and the machine operates like normal. I can get into BIOS and there is a 5-10 second delay from keystroke to reaction on screen. I opened a support ticket with AsRock, hopefully they can give me some insight past "RMA" it. 
 
System:
AsRock Z370 Extreme4 
8700k Noctua NH-U12 (Stock Speeds)
Corsair Vengeance LPX 32GB 2666
GTX 1060 6GB
Samsung Evo 970 500GB
Corsair HX850i
 
Troubleshooting attempted: 
 
Pulled everything apart and put it back together
Cleared CMOS
Flashed Bios
Moved it back to the old location
Yelled at it. 
 
 
 

Moved a completely functional machine about 300 feet in the office today. Once it got to its new home it started taking a solid 5-6 minutes to post. Once it would, another 3-4 minutes for windows to load. Then we're back in business and the machine operates like normal. I can get into BIOS and there is a 5-10 second delay from keystroke to reaction on screen. I opened a support ticket with AsRock, hopefully they can give me some insight past "RMA" it. 
 
System:
AsRock Z370 Extreme4 
8700k Noctua NH-U12 (Stock Speeds)
Corsair Vengeance LPX 32GB 2666
GTX 1060 6GB
Samsung Evo 970 500GB
Corsair HX850i
 
Troubleshooting attempted: 
 
Pulled everything apart and put it back together
Cleared CMOS
Flashed Bios
Moved it back to the old location
Yelled at it.