I've got a new Mac mini with a Thunderbolt display. Most of the time I want to use the speakers on the display ("Display Audio"), but I also use headphones a lot. When the headphones are plugged into the Mac mini, the sound output system preference panel shows "Headphones". However, if I click on "Display Audio", it instantly flicks back to Headphones. Is there a way of changing the output, or am I going to have to plug and unplug my headphones constantly from the back of the Mac mini? This is awkward, given the position of the computer.