Here we go again.
If it's smaller than a breadbox or larger than a cigarette package, the average surface temperature rise of an unventillated box sitting on a flat surface, will be one degree Centigrade for every milliwatt/cm^2 of surface area,
With a plastic box, the temperature of the internal surface (ie the internal ambient air)will be higher.
With a cabinet that is intended to act as a loudspeaker enclosure,the ported vent introduced for sound quality reasons serves as an abominable air vent.
The idea is that a switching audio circuit can be made more efficient (ie smaller) than a linear one, but cost considerations can do two things - it will stick both amps in one speaker container and it will substitute linear amplifiers for the lowest-cost variant that must be stuffed in the same hardware.
Then you have to remember that linear cicuits tested at their ratings won't get as hot as the same circuits operated at a reduced output. A safety examiner might miss that nowadays.
