2.5 cubes is not 1.5 cubes.
if you had 2.5 cubes, why not make the thread "sealed enclosure 2.5cu/ft or less?"
Anyways, long story short, these people give advice to those that could actually use it.
And while those audiopipe toys can make loud noises... So can i by slamming the car door on your skull multiple times, but i bet the distortion levels are horrendous, just like the damage would be to your face.
Loud is one thing.
Loud and clean is an entirely different concept that most people haven't experienced.
And anyone can go loud if they are aiming 50hz up. try and do 140dbs @20.