If you go the Ebay route, the price isn't bad... But people can literally hear my servers on the phone (1 adjacent wall) if I fire all of them up. Also, power draw was crazy - each blade chassis pulls 2500w-3000w !

SBC based stuff is plenty powerful for most stuff now, MUCH cheaper then Nucs, and SILENT! (Great for my sanity)

Some of it is quite quiet nowadays, when not under load.

I can hear my racks but they're about as quiet as the furnace until I do a really big compile.

On reboot they go into full speed fan mode until the controller comes online, that sounds like a jet taking off.

It is, mostly, but if you’re handy with a soldering iron, you can easily solve that problem with a lot of equipment as long as you have good airflow and cooling where your rack is located.