I have 99 Seville STS with factory installed Bose system. I"ve read posts for 2 days now. I have distortion from the dash speakers. When I fade to the rear only, it sounds good so I just keep it faded to the rear. I contacted Bose and they will sell me the 3 dash speakers for $40 each. I don't mind spending $120 if it fixes it. Before I order them, could the problem be from something else?