Why no sound hardware on JPAC?

[DaveJ-UK]

I should probably be asking Andy this, but why is there no sound hardware on the JPAC?

In the FAQ he says "JAMMA standard is for only one speaker, mono sound. This is one of the reasons the J-PAC does not contain a sound amp. Other reasons are:
There is no readily available 12V supply. Using the available 5V supply would not enough power.
Using a separate mains adaptor would create issues with local line cord types."

Surely all JAMMA games use the 12V supply to power the audio amp? I built a little amp using the LM380 chip and that works great connected to a JAMMA finger board.

I want to use the cabinets mono speaker rather than ripping apart some cheapo PC speakers, so should I solder on to the 12V pin on the JPAC (probably not such a great idea) or will the 12V line on the PC power supply suffice?