My son has a 2006 a4. I would like to buy for him a new stereo/speakers/amp. I am having a hard time finding out the specs, especially for the speakers. How many does the car have? What size? I am planning on buying a Pioneer DEHP5100UB SCD receiver because I was told it is a good unit for ipod compatability. I am buying online, so I need to have the information before ordering. Help!