Well you can use mpd for remote playing, but it works like this: you set up the mpd server on one computer, where your mp3/ogg collection sits, and then you can use a mpd client (such as sonata) on another computer where you play the music.
It all depends on where you want to control the playback - on the server (where the music library sits) or on the client (where you have the speakers connected). If you want control on the client, mpd is your buddy.
If, on the other hand you just want a dummy pc with speakers connected and you want to control what's playing from another pc with the music library, then you should try icecast I think, although I haven't tried it yet.
Or, a third way, you have the library and speakers on one pc, and just control everything from a different pc. This would be best done by an mpd config where the client and the server are on one pc (the one with the library and the speakers) and you just ssh into it and use a console client to just control the music (console mpd clients: mpc, ncmpcpp - my favorite).
I can think of another config: one pc to control the music, one pc with the speakers and a third pc (NAS most likely) which holds the music library in the network - this is easily doable with mpd too.