As for this thread:
The numerous chambers, extra walls, and all the extra port displacements - that would be the - THE - prime reason for absolutely NOT doing a 6th or 8th order anything... or even a 4th order bandpass, unless you really are loved doing something unusual or had a sub that made chainsaw sounds that you wanted to mask.
"Small box sub" is what you need, especially in a truck that's probably got plenty of alternator left for a 1000w sub amp.
Vented or sealed depends on your tastes - it's surprising how much output you can get with a specifically high-excursion sub. Finding a high-excursion sub that has significant powerhandling and is a small box sub... challenging but doable. Of course, in those threads we could play with what you already have, so start those for sure, IMO.
But is this a real problem? Or are you problem solving a problem that doesn't exist, which could come at great cost - opportunity cost, performance cost, money cost...
The response of an ABC box - it's NOT flat. That's only OK when you are in a car or closet, and your cabin gain is high enough that it flips that angled response into a flat response.
It's surprisingly trick in a car.
In a home where you will just end up with a non-flat response - there's other ways.
There really are reasons you don't see these often in car audio, and never see them in home audio.
That boils down to construction tolerances.
You can simulate that in the software.
Take a sealed box and add 10% to the box volume. No biggie. The curve hardly changes. You wouldn't even hear the difference.
Take a bandpass box and "oops" the port wall so that it's 10% off, making the one chamber 10%-ish bigger and the other chamber 10%-ish smaller. Watch your previously nice, flat response turn into a peaky skateboard ramp.
Yes - more construction precision is required.
But also - there's more requirement to actually know your sub's REAL specs.
Because the flip side is - subs are manufactured to tolerances. That means every sub deviates a bit - and so also the specs deviate a bit.
If you have a sealed box, or even vented box - again, if the sub specs are off by a bit - no biggie.
But - if you have your box perfectly modeled using the numbers from the spec sheet, and built that box to absolute precision...
...BUT then your specs turned out to be wrong by a bit - it'll impact the actual response just as much.
So - you can budget DATS, if you want to go exotic into these precision designs:
https://www.parts-express.com/dayton...ystem--390-807