Thanks for the tips. Tap-ins seem a little less then perminant, but if I butcher the soldering effort, they will be a good backup.

Maybe I'm messing up the terminology, but I have a wiring harness to convert the female amp input from the dash into raw wires. Solder RCAs onto that for the source switcher and I'm good.

But I wonder if they make the opposite of that piece: female connector to raw wire; just like what comes out of the dash. Then I could connect the female end to the stock deck and solder on RCAs to the raw wire. It'd let me reuse the stock deck in a two headunit setup, saving me from buying an empeg tuner or cd/radio headunit.

But worst is the power. Can I just join the car's power line to both headunits power lines; in a Y? Or do I need some special "power splitter"?

Maybe I'll just stick to the empeg for now.