Ok, firstly putting a second head unit in means you'll have to play with the wiring a bit... =)

As I've mentioned on another thread, my car didn't have an ISO power connector, so I bought a convertor...
This allowed me to split the power wires for the second head unit out of the wires in the convertor, and so leaving the car wiring in one piece (I only spliced the permanant 12v, switched 12v and ground) I then got another ISO car plug, and put that onto the spliced wires...

So what I ended up with is a Ford plug on one end that goes into the car, and 2 ISO plugs on the other end, one for my JVC head unit, the other for the Empeg Mk2.

If your car has an ISO plug already, then you'll probably want to build something similar, using an ISO socket, instead of cutting the car's wiring...

Anyway, it works for me, can be removed if I sell the car, and with heatshrink and self amalgamating tape looks like part of the normal wiring loom... =)

Jazz
(List 112, Mk2 12 gig #40. Mk1 for sale 4 gig #30, apply within)