Sound fades intermittantly

In my Wifes 02 Firebird, with Monsoon, it sounds like her speakers in the front fade in and out... I have checked all the wiring and it looks good. Anyone have any ideas on how to troubleshoot??? Could it be the headunit?

Thanks

Problems that come and go like that are the hardest to trouble shoot. The POS Monsoon system is ALWAYS crapping out one way or another. I'd say it's time to upgrade to a much higher quality after-market setup.