For the ultimate in routing flexibility and power, nothing beats the MH-8 headphone amp from TASCAM
 
TASCAM's MH-8 is the ultimate headphone amplifier for studio, stage and installation. Each of the eight stereo outputs gets 250mW per side with three switchable sources available. Two stereo inputs can be shared to any of the outputs, and individual stereo direct inputs are available for each of the eight channels. A headphone out can select any one of these inputs, or mix several together. A set of foldback outputs allow you to chain other MH-8s into a system.
 
Wide Range of Input Terminals That Support all Kinds of Inputs Sources
The MH-8 has a range stereo inputs that support various input sources; INPUT1 is equipped with XLR balanced and TRS balanced inputs, while INPUT 2 is equipped with XLR balanced and RCA-pin unbalanced inputs, and DIRECT INPUT from each headphone comes with TRS balanced inputs. The input jacks are also compatible with audio system of facilities, in-store audiovisual systems, and recording studio monitoring systems.