Ha!  I happenned to have those female USB ends lying around anyway.  That USB port in the earlier thread was done quickly after I'd had a Eureka! moment.
Here I've refined the art a little!  In this admin panel, I took the PCB holding the front USB ports and phono ports from the front of the PC itself, and remounted them behind the panel.
I had to extend the wires back to the motherboard, where they are connected with original plugs.  I also ran the sound signal through a  log pot to give volume control.  Finally, I attached an extra phono plug (that I pulled off an old PC speaker amp) at the back so that I could plug in my arcade cabinet's amplifier, or another if desired! 
This cabinet is currently for sale on Australian ebay!   Search for "Betelgeuse Arcade Classics"