The case is almost done, except for the trim, but it's time to hook up the electricals. You'll need at minimum a power strip, but I decided to go with a full UPS to provide some better protection for the computer equipment. I mounted this in the base by using the screw-slots on its bottom, so it wouldn't slide around.
However, this means I need a way to turn the whole thing off; you probably won't want the light on and fan running all the time, even if you shut down the computer, but unplugging the UPS isn't a good solution, since draining their batteries often is a quick way to kill them. I intend to use a remote switch inside the case so I can turn everything on from outside the case.
The computer I used comes with a bracket that is meant for affixing it to the backs of monitors, but I decided to affix it to the side of the bottom section. This keeps it up off the ground enough that it won't get wet in case of flooding, but in an area with a lot of room for ventilation and for the tangle of cables. If I'd used another computer I would certainly have ended up with it on the bottom, and probably still tried to get it up off the ground, but definitely firmly affixed so it wouldn't shift when the case is moved.
Then there's all the cabling, and all the stapling down the cables to make them secure. There's power to the speakers, the cord for the fan, the cord for the fluorescent light, and in my case a power strip for these since they wouldn't reach the UPS on the bottom. The video cable between computer and monitor, and the power cable for the monitor. Power for the PC itself. Audio from the speakers, which in my case went into an audio output on the back of the monitor. The main power cord from the UPS needs to be secured near the notch where it will leave the case, so the door won't pinch it. The cables from the controller also need to run to the PC, though these aren't being secured anywhere, since I want the controller board to be removable.
Once it's all hooked up, you can fire it up and give it a try, and deal with any problems. You will probably want to make sure in BIOS setup that turning AC to the computer on makes it boot up; most PCs don't turn on after getting power until you hit a button on it, which won't be convenient, but can be set to turn on automatically.
At this point, the cabinet is ready to be played. (Except of course for the software setup, but that's a whole other set of posts.) But there's still a lot to do to make it pretty as a picture! Even so, your friends will probably find it very impressive.