Klipsch Promedia 5.1 Replacement Volume Control Pod (with Arduino and Remote Control)

Klipsch ProMedia Ultra 5.1 Computer Speaker System

I've got this speaker system. It's called the "ProMedia Ultra 5.1 Computer Speaker System" and it was made by Klipsch, most known for their horn-loaded big concert loudspeakers and home theater speakers. This, however, is a computer speaker system (though it still has mini-horns, as you can see). As it was designed for the subwoofer to sit under a computer desk and the volume control to sit on the desk by your monitor, they went for a wired volume control box. However, I use these speakers for my home theater system (they are certainly loud enough for the job), and the control box doesn't have a desk to sit on.
That little silver control box is connected to the subwoofer (which doubles as the system's power amplifier) by a 10-foot cable with a 9-pin DIN connector, and it barely reaches the couch, and somebody trips over the cord, and it breaks off one of the tiny pins on the DIN connector and then your control pod is useless and things are absolutely terrible.

I set out to fix this, by replacing the control box with an Arduino, and enabling myself to control the whole system with a universal remote I had lying around.