Maybe something like this?
Personally I prefer workstations. They might not have as high of a compute density as a rack server, but you can properly cool them so they run silent and there is less proprietary components. I got a good deal on two of these D20 Workstations Refurb.
Then I installed this 120mm CPU cooler on each CPU, replaced the case 120mm fans with some silent ones.
And these machines are basically silent under full load, they also have room for dual GPUs and 6 HDDs. They generate around 6-7k Boid Power each from the CPUs. Only downside is they are older Xeon CPUs and pull a lot more power than more modern hardware.
I wonder how much power this would give me: Server Rackmount Cases & Chassis for sale | eBay