There are two adjustments on your GMOS-4, if you play with them you might get some sound, I did the same thing in my 06 GP GT w/ Monsoon and ended up replacing everything HU amp and speakers, as the Monsoon amp is a 8 channel amp with it sending lows to woofersonly and highs to tweeters I believe the only full bandwidth channel is for the center dash speaker, as far as the lights go I haven't a clue. Would have to look at your wiring to see.