Help, Im looking at connecting to my factory BA stereo a 4 channel Alpine amp to Run the Front and rear Speakers and then a Mono Amp to run a Single Sub in the boot. Now the issue that I have is that I know I have to run line converters to the fronts and rears but im not sure where to tap the other line converter for the Sub. Do I have to run a line level converter for the sub or can I go from the output RCA on the 4 channel into the Mono amp to run the Sub.