as title above really

i have the standard audi tape chorus headunit with bose setup with bose sub and autochanger, i have bought an alpine headunit cde-173bt Halfords | Alpine CDE-173BT CD Tuner with Bluetooth and need to know which harness i need

i'm confused as to which harness i need as i've been to halfords and they say i need the PC9-401 (but on there website it says its for non bose setups)and i've been to car audio security and they say i need the PC9-408 but it says this on there website 'Note: Use this lead when changing the stereo (and you have BOSE speakers fitted as standard) to a new stereo that has no RCA outputs (i.e. has speaker outputs only)' now the alpine headunit i have HAS GOT rca's, therefore after looking myself i think i need the PC9-410

also what is half amplified and fully amplified, what would my s3 be?

too much conflicting info from people and websites all i need is a bloody harness for my new headunit