I have an 04 Land Rover disco II. I have put in a new head unit and replaced all of the speakers. There were all doing well but recently the mid range speaker in the front passenger door is now buzzing and the one in the driver's door is not working at all. I know there is a factory amp under the driver's seat. Wondering if that amp is going out. If so, is there way to bypass that amp and just have the speakers powered by the head unit?