My Pioneer DEH-P7700 has plug on the rear leads that just connects straight into the car. It's on permanent live at the moment so one of my next jobs is to wire an ignition live for it but apparently this can easily be taken from the back of the fuse box where there are spare spade connectors or from using the ignition live to the heater fan control.
If you need any specific info I can look at my wiring on the Pioneer when I remove it at the weekend.
http://vw-golf-mk2-gti.blogspot.co.uk/2014/06/pioneer-deh-p7700mp-aux-input.html
