July 2020 5k Budget Multi GPU Build

[Alias Pseudonym]

Thanks for your interest in my question:

1. Do you plan to put this rig into a server cabinet where noise is irrelevant or do you want to put it into a room where people are working? This mainly impacts choices for chassis and cooling.

This will probably wind up in my shared office, so noise would be a consideration.  I haven't built PC's since water cooling became a thing, so I'm not easily able to guess how much noise it would reduce, but very happy to go that route if it makes cohabitating with the rig possible.  Ideally, if it ran cool and quiet up until it started cracking, that would be fine, since I imagine most of the heavy lifting will be done over weekends.  The least desirable situation is one where it is loud even when idling, or just being used for other research.

2. Do you want to have an option to upgrade this rig (e.g. up to 4 GPUs in total) or do you want to stick with 2? This is critical for the choice of the platform. For 2 GPUs, any consumer platform (AM4/LGA1151/1200) is sufficient. For up to 4 GPUs, something like old Threadripper (X399) or Intels Core X-Series (X299) works well. Some Intel boards even allow up to 7 GPUs, but will require risers due to space limitations.

Upgrading the rig in the future is a possibility,  It is unlikely that we would go beyond 2 GPU's but in that scenario, we'd just as easily be able to swap motherboards and processors if necessary to add more cards, or even cases.  Once we got into more than 2 GPU's this thing would probably go into a rack anyway, so that would basically be a new build with just the GPU's surviving the cut.

Dual Xeons are definitely overkill for a 5k budget.

The GTX 2080 Ti is a good chip but don't buy a FE. You should get OEM-design blower fans instead.

Alas, I have heard that before, but I'm not 100% sure how to judge a good OEM fan, and there are so many non FE cards to choose from, this is where I can get quickly lost.  Do you know of any specific cards you can recommend?

Important questions though: what hash types are you mainly going to attack and do you need options for upgrades in the future?

This is mainly for cracking the NTLM hashes of around 6000 users and service accounts.

The ability to move up to 4 cards would be nice in the future, but if the best overall CPU/Motherboard/Coolling situation limits me to two cards to start, then I can probably swap out the components later to get to a 4 card machine.

Depending on your answers the recommendations for CPU/MB can vastly differ. For example you need to consider the number of available PCIe lanes and maximum RAM (which should be >= VRAM). If you're mainly going to crack stuff like bcrypt or scrypt you would be much better off with fast CPUs instead of GPUs.

This feedback has been great so far, happy to answer more questions if it helps to narrow things down further.