The Rio Central is meant to be a music server, so at the current time, no.

I don't know if they intend for it to be a feature of future software versions or not. Since it can hook up to broadband networks pretty easily, I could see it being reasonably straightforward to implement MP3 streaming on it. So maybe it'll appear in a future software release.

Now, the Rio Receiver is a different story. If I understand correctly, some of the third-party Receiver Servers will redirect a stream to the Receiver. Someone correct me if I'm wrong?