Confusion on installing JBL Basspro hub in 25' CE w/Bose?

I'm looking to make the upgrade to the JBL basspro hub from the non-existent 6" factory Bose spare tire sub, but during my research I've become completely overwhelmed by how to properly install this. There is much more detailed info on how to install with non-Bose systems and the info I can find on Bose system is from older years. This is coming from someone with basically 0 knowledge about car AV.

Where I get most confused is where to tap the factory speaker lines, whether I need a LOC/DSP, and where I should tap those if needed. I'm thinking of installing a LOC (LC2i) by tapping the high-level (sub?) line from the Bose factory amp, then running RCA's from Sub to LOC. However, I see some folks mentioning tapping the signal pre-amp instead?

I'm hoping someone with more knowledge can let me know if this would work and if not, where I'm going wrong. I really want it to be as easy of an install as possible, but it sounds like the Bose system makes things more challenging and I don't know enough to understand the best way to approach it.
 
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