I have a 2006 TL that I bought last July. I had an after market sub and amp installed shortly after purchasing the car. About 5 weeks later my Nav went out and hasn't worked since. Recently my front speakers started fading in and out than completely stop working. I took it in and they said the factory amp went out and that is why my front speakers are not working. Has anyone else had this problem? What are my options for fixing or replacing it?