If you need to distribute sound to more than one musician at a time, then take a look at the Behringer Miniamp AMP800 Headphone Amp.
It gives you the ability to route a signal to 4 different channels each with it's own control. This Miniamp has the ability to power 8 headphones at once so everyone can get their own set of headphones. Each channel has a 6-section LED output meter so you can keep track of the signal levels going out. Using 1/4" outputs, you can use virtually any set of headphones and get crystal clear sound. This design and structure was conceived by Behringer Germany made with high quality components and a rugged casing so your Miniamp is sure to have a long life. Thanks to the Behringer Miniamp AMP800, your monitor distribution needs will be taken care of.
Ultra-Compact 4-Channel Stereo Headphone Amplifier