Ive got the HK system and as far as im aware the speakers, head unit and the fact it has an amplifier are all different to standard. I upgraded my head unit to a kenwood dvd one and you need to get something called a hkenabler for it to work with the hk system. You can get it from
NewMINIStuff.com
If I was you and I didnt already have it fitted I would just get an aftermarket system as the HK is a very good system but you can get aftermarket ones that are better for cheaper.