just got a sony CDX-GT300 (cheapo) headunit for xmas and installed it. the issue i'm having is when it's on tuner mode the audio is fine, but when i put in a CD i get audio only from the front left speaker. i double checked my wiring and such and i can't see a reason for 3 of 4 speakers shutting off in CD mode.

can anyone shed some light on this? is there an odd setting that i'm missing?