I found a nice woofer on amazon:
MB Quart DS1-204 Discus Shallow Mount Subwoofer (Black) – 8 Inch Subwoofer, 400 Watt, Car Audio, 2 Inch Voice Coils, UV Rubber Surround, Best in Sealed Enclosures
You are correct and I agree about speaker replacement only I would add an amp for all of the speakers. Here is a pi of the enclosure : Ford Bronco Speaker assembly. Woofer. Speakers, 10 speaker audio - M2DZ18808H | Lakeland Ford Online Parts, Lakeland FL
For speakers I chose MB Quart Ps1-316...
I have not heard the B&O yet so I can't say what it needs. It has 10 speakers is all I know. not sure how much power the amp has but bet it needs more power and new speakers all around to improve it.
Not sure the price today but I used to own an accessory shop and we computer cut patterns with 3M film and install it for the local dealers with a price break for volume and preloaded lot units. If you are taking it to the shop the dealer uses, they could give you dealer price. I would have back...