I'm trying to get my amp and sub which i used to use in previous cars with aftermarket headunits in, to work with my rns 510 in the golf. Ive been told to grab a speaker line output converter, so i picked on up from halfords, a pc1-601? I'm a complete noobie at this and can't seem to find a straight forward instruction on how to connect this up, wondering if anyone could shed some light for me or point me in the right direction? Like does this converter connect straight to the headunit or to the rear speakers themselves in the door cards? Thanks