E36 HK System...amp? sub?

[DSrugis]

Alright, I recently bought a 99 E36 M3 and it has the HK system. I imagine this means that it also has the HK amp. Where is the amp located in my car?

Also, did this system come with a subwoofer in the E36 M3? Was it an option? If not, can a subwoofer be hooked up to the HK amp?

Thanks.

Dave