Well, got home. Nothing wrong with mplayer, plays fine. But trying to remove -586:
root@fujibox:/# apt-get -s --purge remove mplayer-586
Reading Package Lists... Done
Building Dependency Tree... Done
The following packages will be REMOVED:
mplayer-586* mplayer-686* mplayer-fonts*

The mplayer-686 seems to be some kind of dummy package though:
root@fujibox:/# apt-cache show mplayer-686
Package: mplayer-686
Priority: extra
Section: graphics
Installed-Size: 88
Maintainer: Christian Marillat <[email protected]>
Architecture: i386
Source: mplayer
Version: 1:1.0-pre3cvs20040323-0.0
Depends: mplayer-586
Filename: dists/unstable/main/binary-i386/mplayer-686_1.0-pre3cvs20040323-0.0_i386.deb
Size: 37398
MD5sum: fef26c9df121f14a7bb1672a1947c71b
Description: transitional dummy package which can be safely removed
Dummy package to upgrade to the new package mplayer-586