I had one of the (now 2 gens) old Z6xx series workstations issued by work, and I ended up buying a second hand one from eBay to replace it when I moved jobs. I

I had one of the (now 2 gens) old Z6xx series workstations issued by work, and I ended up buying a second hand one from eBay to replace it when I moved jobs. It was dead silent. I could hammer all the cores, RAM and disks, and not hear anything from it. At one point I had 4 of them under my desk, and there was more noise from the MacBook Pro.