Lesson 1: Marshall Class 5 and I were just made for each other.
Lesson 2: The Marshall Class 5 and its built-in speaker were made for each other, because it sounded really shitty when I swapped speakers with my Vox AC4, which has a Celestion G10 Vintage. That just made both amps sound like shit. The Marshall Class 5 is really, really good stock, even comes with a JJ EL84, though I swapped with an EH just because.
Lesson 3: Marshall doesn't know how to build tube retainers, apparently. The built-in one sucks, I just took it out.
Lesson 4: Unrelated, but Scumnicos are wonderful: