1. The first section is specific to ubuntu - xubuntu, kubuntu, lubuntu users will not have nautilus installed. Its also possible that installing nautilus-terminal will also install nautilus (unable to verify) which might cause problems on some (ie. xubuntu). Perhaps specifying that these instructions are for ubuntu only or adding similar instructions for the other spins.
2. In addition to sox, I would also add mpg123/mpg321. The nice aspect of this player is that:
...will repeat-random play all files that match that pattern. Ctrl-C to skip to next tune, Ctrl-Z to pause, fg to un-pause and 2 Ctrl-Z in quick succession to quit. Unfortunately, it lacks some other abilities like previous, forward/backward x frames, etc, but is a quick, small player. It can also stream online radio via something like:
mpg321 -Zz ~/Music/*.mp3
...(dubstep radio station in the example above)
mpg321 -vC http://22.214.171.124:80
3. And as suggested by sysaxed, there are also ncurses-based music players. They are lighter than their graphical cousins, but offer more control and functionality than just the command-line utilities. If you choose to mention them, in addition to moc, you could add cmus, mp3blaster, cplay. I'm not sure about moc or mp3blaster, but both cmus and cplay have remote control utilities that you could assign to shortcut keys and be able to manage the playlists in that manner.