Ok, finally managed to remove the concert and got my new unit plugged in using PC6401 adapter. At first didnt get any rear speaker sound but quickly worked out i needed to connect the blue wire to my HU's amp switch output.
However, the sound still sounds a bit odd from the rear, not quite as good as it did with the concert....i may be going mad but i think i remember reading a thread on here (that after half hour of trying to find i can't) where it says it will sound not so good due to the rear speakers running from the HU speaker outputs rather than rca's....is this correct? If so shall i just get a rca to speaker output adapter and splice that into the loom so the rears run from the HU rca's?
Hope that makes sense