Ha! I’m tempted. So far, adding the sub has made a HUGE difference though.
No, just the one for now.
You have to pull the whole speaker box to do it the first time, you can't just remove the grill from the front, so it's more of a pain than you might be expecting. Plus, I don't think the new speaker sounds any better, it's pretty much the same.
There are extra grill retaining screws INSIDE the box. When I installed the new speaker, I just left those un-attached and threw em in a bag in the coin box. They really aren't needed.
(Also of note... Taito does not stock the regular Vewlix speakers anymore, so that path is a dead end for replacements)