isn't pulse a replacement for esd? i think it should be in extra, yes. there is a request for mpd to be compiled with pulseaudio enabled:
http://bugs.archlinux.org/task/8472 if you move it, let me know so that i can make mpd support it.
Jan expressed an interest in pulseaudio in the bug tracker,so lets leave it to him. I don't know much about pulseaudio anyways.