Building a multi GPU rackmount server

[dfns]

I want to build a multi GPU (3 to 4 GPU) rackmount server to support cracking NTLM (-m 1000) hashes for my team of pentesters. My budget is 20k max. Any suggestions on hardware selection? I've been looking at Gigabyte servers and I think I need a 4U profile to mount the cards vertically. 

Going down this rabbit hole and googling this is starting to create more questions than answers. For example, I'm reading about FE cards with radial fans and heat, and it looks like the RTX 3080 Ti cards I had in my shopping cart will have one of two fans blowing hot air back into the case.

Heat dissipation and power supply are a big concern so I can avoid burning down the data center or shortening the life of the system due to heat.

Thanks in advance.

The only RTX30xx blower style cards are from Gigabyte (3080 Turbo and 3090 Turbo) and Asus (3070 Turbo, 3080 Turbo, 3080TI Turbo, 3090 Turbo). The sweetspot are 3080 cards, they deliver about 100GH/s and costs about 800€, the 3080Ti (1200€) makes 117GH/s and 3090 (2000€) makes 125GH/s. For 4x3080 (4*320=1280W) you need at least a 1400W power supply. With 3x3080 Turbo in big tower (Meshify 2 XL) the cards runs stable over weeks with about 88-89°C, that wouldn't be possible in closed case with axial fans.