Hello, for two days I have been a freshly baked audio owner, an a4 avant 1.9TDI. with the car I am highly satisfied, only the sound still makes me worry. it is a radio chorus built in, which I want to keep, because it fits a) well into the armature board and b) the original audio accessories is too expensive for me. however, on better sound I do not want to do without it. first of all new speakers have to come here, at the front I have already built in a 13er system, still missing an active sub. and that brings me right to my question: have the radio not yet expanded, does it have a pre-out, to which I can connect an active sub? In order to the invisibleness of the tuning measures I wanted to get a blue point THB200A, which then disappears under the seat. maybe I would also get an active box for the suitcase room, however, should then in contrast to the blue point also mean a clear sound improvement. a passive sub-solution comes not t in question, because I have no desire for large-scale construction work and at level is not my main focus either.