The signal at the front midbasses was full range/unfiltered in my 2022 Highlander Platinum (similar JBL ugraded system). I pulled the bass signal from those and it was more consistent and hit lower than the stock sub. Worked really well.
Not sure if the 4runner premium system is similar, it...
Anyone thought of installing molle rear side window panels and a molle shelf across at the top.... then install amps on that shelf?
https://caliraisedled.com/products/rear-molle-overhead-tray-for-2025-4runner