You need to find something that is made for microphones and live music - not a home theater system - something like a PA system -- a cheap one can be had for around 150.00
"This affordable Harbinger HA60 PA System features a mixer with 4 mic/line inputs, 2-band channel EQs, digital effects, an AUX input for MP3, CD, or computer connection, and a direct output for recording; 2 - 10", 2-way full-range speakers equipped with stand mounts; and 2 - 20' speaker cables. Additional features include an AUX input for MP3, CD, or computer connection and a direct output for recording."
You would plug in the output from your box into the AUX input of the PA system - then can have 4 people singing and mix in the music from the player...
Edited by Martino, July 14 2013 - 11:25 AM.