Audio was pretty simple. I needed to channel the audio through some middle-man to get the car speakers amplified. The amp needed to handle 20 watts per channel, have an RCA connector audio input and have a hard power button so it will power on and off with the cabinet. I found a small amplifier with no vents or major heat emissions made by RCA, the SA-155. Found it on eBay for a cheap price. The seller even threw in the headphone to RCA cable converter to connect the PC audio output to the stereo RCA input.
The next plan was to be able to control the volume from outside the cabinet. I knew it had to be via the speaker wire and found a great piece at RadioShack that controls a pair of in-wall stereo speakers. I sanded down the plate and the knob and spray painted them black. They came out nicely.
Once the speakers were installed in the unpainted cabinet, I hooked up the speakers via 16 gauge standard speaker wire to the in-wall volume control and, in turn, the in-wall volume control to the amplifier. Rather than hook up the PC to test the sound, I found an old cassette deck and an old mix tape. Everything was turned on and the speakers worked perfectly. I knew I was ready to roll on audio.
You just need to hook the PC's sound card output to the amplifier input and set the amplifier volume to around 50-70%. Then, control the volume from the control knob.
I also suggest disabling any sound themes in Windows XP to make the bootup and shutdown silent.
Here is a shot of the speakers mounted in the cabinet...
Here is a shot of when I hooked up the cassette deck to test the amplifier and speakers...
Another shot with the amplfier placed in the cabinet. It's not secured in any way, just laid on the floor and accessible through the Coin Door.
This is the volume control on the top of the cabinet. The painting looks much better than this picture. The flash washed out the color.
Inside views of the speaker volume control box. The brown and white wire pairs go to the speakers, the two black pairs come from the amplifier. The other white wire is from the marquee light.