Hey, new to this so it's a steep learning curve. Anyway, I have a 2004 320i Canadian model with non HK system, I have the business cd setup. Now I was wondering if I have a factory amp or does my factory business cd power my speakers. I suspect that it does it internally rather then having an amp like the HK system. What is the best way to use my OEM HU to install two amps, one mono channel to power a sub and a 4 channel to power my front and rear speakers, and what products would I need? If this cannot be done how would I connect an aftermarket stereo to my car, would i need a wire harness, and if so where would I get one for my make/model of car. Also, where would I get the pinouts and wiring info for my make/model of car. Thank you in advance for any help you could provide