Thanks for sharing Rich. Yep - I'm planning on upgrading the audio in my TGH as well. I haven't purchased one yet but plan to next year (unless I'm just blown away by the Hyundai Palisades Hybrid or the KIa Telluride Hybrid (the Hyundai is scheduled for 2025 but the Kia is still up in the air). My girlfriend drives the RAV=4 and has the "premium" JBL but it has only rudimentary controls (as you point out) and there is only one woofer at the back of the vehicle. My understanding is that a woofer should be placed closer to the driver and an external amp is a serious upgrade. You now have me thinking also about upgrading the speaker system too.
Regards sound proofing, I've seen videos of soundproofing in the doors, beneath the floor mats and even under the hood. Supposedly there are shops in Europe that do this all the time, but here in the States, its mostly car audio shops that make this happen. My understanding is that once done, the sound proofing is more noticeable when driving on highways but that in town the result was marginal.
Thanks for recommending an amp - I'll definitely check that one out.