Welcome to Club Polk entgegnen :smile:
While the deal cody has led you to would save you substantial money, unfortunately your HK doesn't seem to support 4 ohms as the user manual only refers to 8 ohms in the tech spec section;
http://www.harmankardon.com/resource...Manual_Eng.pdf
I often had to repair amps, receivers and AVR for the simple reason of improper speaker impedance matching with the equipment. Eventually you wind up blowing the output chip so I would suggest you check for speakers that have the appropriate ohmnic value for your receiver.
Now, your first step should be to check all those pre-wired runs to make sure they are suitable for your install. Check for potential shorts and-or opens. Once you have determine this cabling is suitable and ready to connect your AVR to your potential speakers, you can then search an audition speakers of your liking for the install.
Again, welcome to Club Polk and happy speaker auditionning :smile:
TK