My friend is completing his online audio shop and was wondering what are the most popular upgrades to the A4. He will definetely have the best prices anywhere, so your help will be rewarded.
Thank you.

The following aftermarket audio upgrades work with the Concert head unit. Not sure what will work with the new Symphony units.

Panasonic 6 and 8 disc cd changers and adapters
Speakers
MB Quart speaker mounting brackets
Amps

Head units

Regards,
Rodney

'99 A4 1.8tqms