I have a headless Ubuntu server running in my basement. It streams to my PS3 using an app. called MediaTomb. I use this same box to manage torrents using TorrentFlux.
Hardware is an OLD 1GHz processor and maybe 1GB of RAM. I haven't touched this PC in months, it quietly runs and when I do need to access it, I just use PuTTy to logon remotely for all administration.
MediaTomb can be a little intimidating to get configured, but there are several different walkthroughs available. Good luck, it's a fun project!
If you can spare $15-20 a month and are somewhat Linux-knowledgeable you can: