I’d say the speakers are right.
Not too sure about the red being +VE. It may go to a switched live, which isn’t really needed. The brown wire is the always live I use for both switched and non-switched live. Only trouble I get is the fuse pops if I have loud music and use the cig lighter.
About the ISO – if you don’t use one and cut off the head unit’s one the guarantee will probably be void (like mine is) – so I’d recommend hooking in the ISO.
I think the cable you linked too isn’t the one you need as the original FIAT connection is missing :confuses: - AH the second link is more like it. Maplin are cheaper
http://www.maplin.co.uk/Module.aspx?ModuleNo=19651&TabID=1&source=15&WorldID=&doy=26m4
Or http://www.maplin.co.uk/Module.aspx?ModuleNo=27994&TabID=1&source=15&WorldID=&doy=26m4.
Good luck!
Regards,