I have a non-bose Symphony system on my 2006 A4 Cabriolet that sounds like a bad tin can. This car is new to me and I absolutely cannot believe Audi would sell this stereo. It is the WORST stereo sound I've had in any car I've owned. Anyone have any thoughts on what I can do to upgrade the sound? I've already replaced the front speakers and tweeters, but now I have absolutely no bass in the car. What is available for this? Also...I've tried to get to the "hidden equalizer settings" that is discussed in some of the A6 threads. But, there is no access apparently from my head unit (I tried holding down the 5 preset key and then turning on the head unit to no avail).

I am desperate here. I really don't want to swap out the head unit, unless necessary. I am contemplating some coaxial rear speakers and a small subwoofer. Is this what it will take? Or is there an easier path?

I still cannot believe the crappy sound. The head unit barely changes anything when you scale up or down the bass, midrange, or treble. Unforgivable, in my opinion, for a $33,000 + car...

Thanks in advance for any advice here...