Recommendation for building a Hash Cracking Rig in 2020?
Any specific hardware recommendation to build a simplified Cracking Rig considering to start with one GPU and after that add as a minimum two or maximum four GPUs in the long term? I want to put together something that is easily compatible running Ubuntu 20 LTS with the primary goal of cracking mode 2500 hashes. Preferable Intel and Nvidia to fit in a Fractal Design D7 MidTower and ideally as silent as possible. The GPU or MB needs to be USB-C compatible with operating two LG 4K panels (24MD4KL-B). Looking at Nvidia RTX 2080 & Intel MB socket 1151 with intel 9th gen i7 or would one recommend lower-cost CPU, e.g. i3 without losing any cracking performance? Looking at a modular PSU Corsair HX1200i 80 plus platinum series. Ideally no water cooling in the build but a Noctua NH-D15 CPU cooler and enough fans in the cabinet. 

What would the ideal motherboard and components be? 
  • Nvidia GeForce RTX 2080 Founders Edition? Any reason why the MSI GeForce RTX 2080 Super Ventus OS OC will be an issue or less optimal than the "Founders Edition" version? 
  • Motherboard?
  • CPU? 
  • M.2 disk(s)? 
  • RAM? 
I have been looking at ASUS ROG STRIX Z390-H GAMING, i7-9700K, Kingston A2000 500GB NVMe M.2 SSD and Corsair vengeance rgb pro ddr4 3200mhz 16gb. Not sure if that's a good setup so I would appreciate some first hands experience recommendations.

And lastly, is it worth going for the 2080 Ti version or wait until any 3080 release later in 2020? Starting with a 2080 and then adding a 3080 should not be an issue having these operating together? 

Thank you in advance, 
Since the 2000 series FE cards are no longer recommended because they don't have a blower fan any longer and thus are not suitable for stacking multiple cards in one case.

For RAM the rule of thumb has always been RAM >= VRAM. Also I would recommend to have at least one CPU core per GPU.

The hardware you have listed sounds like a solid base for a small rig. Make sure you pick a case with good airflow (front to back).
If you are going for more than two GPUs, I would recommend some HEDT platform like Intel's X-Series or Threadripper, since most consumer grade CPUs will run short of PCIe Lanes. If you want to get the most for your money, you should go for something like a 1900X Threadripper with an ASRock X399 Taichi. For Intel, something like a i7-9800X and a Gigabyte X299X AORUS MASTER looks decent. Note that these mainboards actually have the correct spacing of PCIe slots to support 4 GPUs.

If you run long cracking jobs, there is basically no chance to keep things silent and cool at the same time, unless your room temperature is really low (and will stay low) or you dont use the full capacity of your cards. This is especially true, because you want blower-style fans on your GPUs for a good front-to-back airflow, as undeath mentioned. Some good design that was already recommended here are these ones from EVGA: (seems like epixoip bought all of them, couldnt find any that are in stock lol)

Waiting for the next-gen of Nvidia is definitely a good option, although it looks like the upcoming FE cards are again with axial fans, i.e. terrible for stacking. Lets hope there will be a good OEM design.
The 3080 supposedly has the same or similar amounts of cuda cores as the 2080. Would you still recommend it?
According to these rumours, there will be some improvements though:

Also there is apparently some AMD flagship on the horizon:

I think they will be some interesting products, but in the end, it depends on whether you wanna wait until this actually releases later this year or not. In case you want to build now, have a look at this thread