I am going to improve my stock HK audio system. I've heard that a/d/s provides amplifiers which connect to the stock head unit. Further I've heard that a/d/s is going to provide a replacement for the stock subwoofer unit. Does anybody know about this or has experience to share. A phone number of a/d/s would be greatly appreciated (no 0800-, 'cause I am living in Germany). Many thanks for your help !