What do you do when you want to use your expensive, high-end headphones with your MP3 player, but you can't get enough volume out of them? The Boostaroo Revolution ($79.95 direct) is a small, inexpensive headphone amplifier that significantly boosts your MP3 player's volume and provides two 3.5mm headphone outputs so you can share your audio bliss with a friend. The bad news for audio purists: An onboard processor adds 3D surround-sound imaging. The good news for everyone else: If you have high-end headphones, this device will help your portable player (or laptop) drive them without your having to turn the player's volume up all the way, thus keeping distortion down and saving your player's battery.