Aux in naming is so that you can name the device. For example if you had a Sony CD player as the Aux-in, you could name it "Sony CD".
The Quit menu option is only useful if you are a software developer and you have created an alternate INIT file or a shell script that gets run whenever the player exits to the shell prompt. For instance, before Hijack was available, I used the Quit option to exit the player and run a "picker" shell script that allowed me to change whether Voladj was on or off, and also I could choose to play Tetris.
The reason Quit seemed to lock up your player is that you didn't have any programs set up to run when the player exited. So it just dropped to the shell prompt and waited for you to type something at the shell prompt.