Late in 2004 a friend turned me on to a toy from SlimDevices.  This allows web access to an MP3 player that plays in the house audio system so it can be controlled from virtually anywhere and uses a central file server for the MP3 source.  That means every PC in the house has access to the same MP3 archive and the size of the MP3 database is only limited by the disk space on the server.

It also means that Mary can control it (via Cliff) via http or even it's own network interface.  Playlists can be built on the fly and are stored on the server.  The server side of the software even goes out the internet and looks up artwork for the CDs if the MP3 tags for the album indicate where to find the artwork.

The only down side I have observed is the server seems a bit processor hungry (at least for the Windows version) and in later revisions only gets worse.  The problem only shows up if the server is asked to change playlists, provide statistics or something else CPU intensive.