Thanks guys!

Upon further inspection I've found that the amp is only driving the two subwoofers in the back. I'm going to have to use a head unit for the Empeg's amplification, though a different one than the one I have in there as it doesn't have AUX-in without a silly adapter. I've still got the old head unit from the last install so I'll throw that in first, make sure it works, then hook the Empeg to that. I'm pretty clear on the wiring now, and provided I didn't destroy my sled wiring in the process (I used too much solder on the loose pin and heated it up once or twice more to get the extra off) I think I have soldering under control. Either way, it'll be a better job than the twist the wires together and electric tape job that he did.

Edsmiata:
I did read your previous posts but was unaware that you still had the problem so thank you. I don't have AC but we'll see if it happens with the vent or headlights.

He had the sub put in two boxes in the trunk. Never having owned one before I can't see how that works well with the trunk closed, but I haven't had much of a chance to try it out yet, what with spending 20 minutes trying to get those eye-vents out.