Hey guys so my sons r58 has the standard sound and my r56 has the HK which is much better. I was thinking it must be possibly to find used HK parts and upgrade his sound.
1) what do I need amp, speakers maybe a harness ?
2) is the coupe a different setup from the hatch ?

 

Speakers, additional tweeters, A-pillar trim, amp, different left hand trunk trim, mount plate for the amp are some of the items needed. Whether or not any harness' is required I don't know. The radio will have to be coded (so that it doesn't send filtered sound to the rear). Whether or not more coding is required I don't know.

However, given that the above items alone cost far more than a pretty good aftermarket sound system (I'd even suspect that they will cost used more than a new aftermarket amp and decent front speakers, let alone used ones) I don't see the point in going that route. Especially given the fact that HK amps like to die prematurely...

 

Check out BAVSOUND speakers. I believe they have a base model option. They HK speakers are fine enough, but the upgrade is worth it.

 

Do aftermarket.