iamdub
Full Access Member
I don’t believe there is a line out signal to the Bose amp, at least not one that can be used without some sort of converter since Bose uses proprietary systems that don’t always work well with others, like aftermarket stuff does. Thus why most people swap out the head unit. Not only do you get cleaner and more bass, but you gain a lot of adjustability with a dedicated sub out signal. It just sounds so much better.
Aftermarket HU 100%.
IIRC, there are two styles of Bose HU/amp systems. With one style, the HU sends a full-range analog signal to the Bose amp. You can intercept the channels of the full-range signal before it goes into the amp to connect that to your aftermarket amp. My original plan before I wised up and got the aftermarket HU was to tap some female RCA pigtails to these wires.
The other style of Bose amp ("Lux"?) has a digital signal sent to the amp and it processes everything, including the volume level. So you can't just tap into some wires.