I'd go with Fedora if I didn't want to mess with config files. It comes with networking tools with can do some stuff for you, but as always, to unleash to full power of Linux, you might have to tinker under the hood a bit. For max performance, disable xdm (or kdm, gdm, etc, the program that starts the GUI automatically at boot) and only launch it when you need to use it. No sense wasting cycles rendering X11 on a server.
Alternatively, you could sell the computer on eBay (they're selling for $135-$450) or Craigslist and buy a x86 computer of much higher power with the proceeds. This route would allow you to choose from a bigger selection of distros.