That's weird that you have a left and right channel speaker out... and on different sides of the car! Is it possible that you overdrove the speakers and blew them out?
My recommendation would be to replace everything and get a new head-unit, amp and speakers. That should solve the problem!
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1998 Camry LE V6 --- 149,900 miles and counting...
Jobs done so far:
- CDT Audio speakers / - Alpine CDA-9851, KCA-410c, & KCA-420i / - Hawk Brake Job
- SilverStar Headlights & Signals / - Tokico Struts & KYB Strut Mounts