I got my first Acura TL (w/ Nav) and like most people, want to upgrade the stereo. I've been doing searches on here and on Acurazine to see what others have done. I plan on keeping the stock HU. After reading, I plan on getting an AudioControl Matrix for sound processing. The ACM takes rca's for it's inputs. My first question is, do I tap into the factory wiring before or after the factory amp and convert those into RCA's and run it to the matrix?