You could also try finding a more or less silent PC. I don't have experience on different hardware, I just use what I can get my hands on that gets written off at my work, but I have very good experiences with Dell PC's: they all work very well with Linux, they're pretty silent (especially the business models like the Optiplex or Precision) and they are reliable and solid. You could also try placing the PC in some sort of silencing case.