I had exactly this problem, 1U server that sounded like a 747 taking off downwind. I solved it by getting a mini-PC that had more processing power than the eBayed 1U server (I just looked up what was available in terms of CPUs and got the best bang per buck, an 8C16T AMD CPU) and that runs essentially silent except when it's under load - they're designed for low-power/silent operation. If you're running your server at 100% load 24/7 then this isn't for you, but for home "server" use it was ideal.