A growing music collection demands a powerful media player. While VLC will play just about anything you throw at it, it seems to choke regularly on larger libraries. I'm giving Quod Libet a spin for now:

# apt-get install quodlibet quodlibet-plugins

(The plugins aren't strictly necessary, but they include some nice features like album cover grabbing and automatic rating systems.) So far, the experience is pretty seamless, though I've only got about 2000 songs loaded into the library; I'll be chiefly looking for scalability as I put my 1.5 TB RAID 5 to good use!