Intel sells boxes they call NUCs. I'm running fedora on one at home seems to work fine (as a media PC). Asus makes similar sized bookshelf systems. A lot of them come with Windows forced down your throat, I got a NUC without memory or disk and added my own.
Lookup mini PC on amazon for a vast selection.
I'd think centos would be better for a server-like system since it has a longer lifespan, fedora goes out of date really fast.