Have anyone experince power lost in volume. I have an 2011 nox LTZ with NAV and the volume seems not to have the power it use to. I can turn it up mid way and if it had a dail from 1 to ten, mid way would sound like a 2. Before, mid way would be too loud, base would shake the whole car. Is there an issue with the amps going out on the radios? Thanks for any response.