Ice advice please

how can an SOT lead cost that much?!
try http://www.co-star.co.uk, if its not on the site, give them a call, theyre only about £5!

Definately wouldn't recommend trying to use an Alpine HU with the Bose system unless you are planning on ripping out the speakers and Bose amp. You'll get all sorts of popping and noise issues trying to integrate the new HU with the amp, plus the quality of the new HU will be totally compromised by the inferior Bose amp/speakers so very little benefit soundwise and it could possibly sound worse.
If you just want more functionality then fit a Becker which integrates properly with the Bose system and will give you mp3/iPOD/USB etc. Looks totally stock too.