Anyway, I've been stuck for a little while now on how I should go about mounting my speakers into the arcade cabinet. They are supposed to hang down from the top of the cabinet through the bottom of the marquee, right in front of the monitor. Well, I bought a cheap, yet good, 2.1 speaker set by Creative Labs. It has a subwoofer with 2 satellites and a remote volume adjuster. The sub is going inside the cabinet with the computer, and the satellites will be installed as I described above. However, removing the speakers out of their casing will be detrimental to the sound quality and don't have any great way of mounting them. After over a week of being stumped over this, Juri's wonderful creativity saved the day!
Here is a picture of her idea:

If I take a strip of MDF and go across the middle of the speaker panel of the cabinet, and glue that brace to the speakers, it should hold on to the speakers pretty well. I may have to sand the speakers where the brace will glue to it to hold it properly. I'm also going to have to disconnect the wires from the remote volume unit to be able to run the speaker wires through the middle of the brace. Once I cut holes in the speaker panel to place the speakers into, I will mount the speaker brace to a hunk of MDF to elevate the height of the speakers. Also, in the event any light tries to leak out from the marquee through the holes I made in the speaker panel, I can use some black felt to block the light out.
She's a genius! I love my wife!