Do you currently have or are you planning to have a surround-sound setup? A passive sub will not work with surround sound because your receiver will not know a sub is connected, and will therefore not know where to send the bass signal.
If, on the other hand, you have a stereo-only setup, then I'd suggest putting the sub in-line with the front L and R speakers. Speaker wires should run from the receiver to the sub, and then from the sub to the speakers. Your H/K amp shouldn't have a problem with it.
