What a bummer. Something like an 80PLUS Platinum ATX PC PSU could do around 40 amps on the 5V rails. Redundant server PSUs seem like an obvious choice here.
if you're using amazon.com/dp/B077R5BVVR/ removing just the outer enclosure and removing that fan should be safe, but it might not be the loudest fan...
otherwise the quietest PC is the one in a different room, but you probably already know that
That's exactly the one I'm using, thanks! I was considering the fan, but I've also been worried about torching my house. I'll give it a shot.
I put some work into the frame the cluster is in, and it makes a pretty nice end table. My main pc is a little fanless industrial computer and I love it.
For USB power? I don't think there should be any way for Pis plugged into the same freestanding hub to talk to each other, but if so you could prevent that with power-only cables.
Call me paranoid (this is about security after all), but there's no visual distinction between data and power-only cables. While a rogue employee can wreak all sorts of havoc in any data center, it's nice to have as many correct-by-inspection systems as possible.
I don't see why one couldn't get a power-only hub, but I couldn't find anything that appeared to be high quality in a quick search. I did find some pretty nice looking rack-mounted kit, but they all appear to be data hubs.
Though either way you might be better off with a series of USB hubs.