Thanks to everyone's suggestions, and against my better judgement, I crawled behind the dahsboard and found that a yellow wire was connected to a red wire, and a red wire was connected to a yellow wire. So I cut both wires, and reconnected them so that red went to red and yellow went to yellow. Now the Empeg comes on and stays on all the time, and when I start the ignition, a little "battery" icon appears in the top left corner, and the Rio Car still doesn't come on. I'm going to try to get to the fuse next and see what that looks like.

I'm really regretting where I took the thing to get installed now.