On a mono sub amp for subwoofer update on 05 X5 with nav and no dsp.

Reading all this, it seems that there are three basic ways to deal with the inputs to the sub's new amp:

1. Tap into one channel, say Lt, and connect the +&- to the amp's hi-level input plug wires.

2. Do the above, but use a line converter so you can use the RCA jack low-level inputs on the amp.

3. Connect all 4 wires from the +&- of both channels to the appropriate wires on either the converter or the amp's hi level plug.

Now the questions:

1. Are low bass signals the same Lt and Rt, so that it wouldn't matter if only one channel was tapped, or is there an advantage to using both Lt and Rt channels to source that bass?

2. If only one channel is tapped, do you combine the wires on the amp, or the input converter, so that both +s and both -s are used?

3. Is there any particular advantage to using the converter and the lo-level jacks?

I ask all this because all of these connection options are recommended by various contributors to this fine site! And because I hate the smell of electrical fires in any vehicle I own.

Thanks, Carl