Amarok is one of the more popular music players on Linux. By default, it uses SQLite to manage its database of songs and playlists. However, there is a way to speed it up by using full database back-end such as MySQL and PostgreSQL.
Here's a short but useful blog entry on how to setup and configure MySQL for Amarok.
Now, if only you can do the same for e-mail clients, it would have been faster and easier to archive.