...but can't seem to find it. I want to replace probably all my speakers in my B6 A4 (2003 3.0 Quattro). Currently I have the non-Bose symphony.

I know the 8 speakers in the doors consist of a 5.25 inch low/mid and a tweeter (each door).

But I can't find the answer to -- what is the speaker in the trunk? Some kind of cheap subwoofer? A coaxial two-way speaker?

And -- is there a small center speaker under the grill in the center of the dash?

Thank you if you can help me with these questions, O good people of Audi Forums!!!!!

 

Yes there is a cheapo sub woofer on the rear deck on non bose models. I would just upgrade all the door speakers and deck speakers with quality ones, and hook those up to a 4 channel amp. Remove the old subwoofer assembly and see if you can jerry rig a better quality sub in that enclosure and run a cheap 2 channel amp to it. Im not sure what the size of that woofer is, you'll have to measure it. If its only a 6" woofer i would just get a new enclosure for an 8"-10" woofer.
Yes there is a center speaker under the dash board, its the center speaker and is driven by the head unit, its basically a tweeter so leave that be.