As the erstwhile alsa-xmms maintainer, I can officially confirm Cameron's explanation: the latest upstream XMMS version (1.2.8) incorporates the ALSA plugin itself, so there's no longer any need for a separate package and you should go ahead and remove the obsolete alsa-xmms package in favor of the new xmms version.
-- Aaron M. Ucko, KB1CJC (amu at alum.mit.edu, ucko at debian.org) Finger [EMAIL PROTECTED] (NOT a valid e-mail address) for more info.