Can anyone offer me some helpful advice at this point?

Seems like you are at one of those junctures in life where you can take the problem to somebody else and give them potentially significant $$$ to deliver a black box solution or grapple with it yourself and perhaps accrue some intimate knowledge of you car's wiring. In your shoes I would probably go to Radio Shack and buy a cheap multimeter -- make sure you have volts coming out where and when you think they should.

Side note:When you say you checked the fuses, I assume you include the Empeg/Kenwood fuses... is your Kenwood also fused in the back? (Mine is) ..