There were some early S2000 machines built with the Vision top box with the hidden speakers. I used to have one. What you describe, having only the right top box speaker and a printer on the left side is a modification. It didn't come from the factory that way. It was converted to a ticket machine. In order to add a printer to the top box, one of the speaker housings had to be removed to make room. This is the simplest way to add a speaker. The other way is to locate the printer to the right of the reels which requires a lot of parts and lots of work. I believe IGT once had a conversion kit for this. New reel shelf, glass, printer mounting parts, etc.
I believe you can add a coin tray speaker. Your amplifier board should be located on the back wall of the top box. I believe the J5 2-pin connector goes to the coin tray speaker. If something is plugged in there, it is probably the harness you need. If not, you might have to buy or make a harness.