pop open that technical note in your first post.
the plot that shows the sealed cab outdoors vs. in car shows the difference of what is called "room gain" or pressure vessel gain.
cars are small, so that gain kicks in pretty high in the frequency, up around 50hz or even higher for a small car.
as a result, down around 40hz, where the big bass hits are for your kind of music, the car is providing 15db of free gain.
your actual room is much larger than a car and so that gain won't be kicking in until around 30hz. so the whole mountain of spl gets wiped out when you move from the car into the home.
in a car, it often only takes 100-200 watts to get up past 120db peaks in the 40hz bass. most folks would consider 120db+ bass hits pretty big, but others would want even more, but it is definitely enough to get pumping pretty good.
in a home, you don't have that big gain, so it almost all has to come from the subs, which means more subs and more power or more sophisticated designs.