Instead, I decided to replace one of the switches (which wasn't working as its solder pads were busted) with an SKCL Lock switch from an AEK and wire the speaker to it instead.
(potato camera warning)
Just in case, I used some electrical tape to separate the SKCL Lock switch contacts from the PCB:

I sliced up one of the speaker's original cables, but on reflection, I should have just desoldered it from the speaker and use it for one of the switch contacts:

Here's how it turned out: Overall, I love this board. The soundtrack, keyfeel and orange LEDs are fabulous, and now I have a way to use it at work for longer than it would take my co-workers to organize a lynch mob
