After actually trying out Songbird, I have a lot more respect for it, and amaroK has always been an excellent audio player, but my favorite media-management program for Linux is still Exaile.

If you've never heard of Exaile, give it a try. It's a lightweight, Python-based media player for GNOME and XFCE. It's supposed to be the amaroK of GTK-based desktops, and it's designed to be lightweight and fast.