If you want to have the coolest headphone setup on the block have a look at this Tube Headphone Amplifier project. When everyone else simply plugs their headphones into a transistor amplifier you can enjoy the rich sound that comes from a tube amp (at least that is what some people say).

"The tube heater draws 150mA at 12.6 and the whole amp draws 580 mA at startup and stabilizes at 550mA after the tube warms up; which takes a few seconds. I used a Canon AD-360U switching power supply from their small bubble jet printer. Since the drain of the Mosfet is connected directly to the positive rail any noise will be amplified. This power supply had virtually no noise. This amp is perfect for the novice builder and the components are available at mouser, digikey. You can substitute other Mosfets as long as the resistance is similar and the internal capacitance does not effect the response curve. It is best to use TINA-TI to build the schematic and make any changes, this way you can check the ac output before building. This will save you much time."