I have Harmon Kardon 3650, which is 7.1 system. I bought a used Polk surround speaker set that included a powered sub-woofer. I already had a powered sub-woofer, but wanted the other speakers to upgrade my system. So now I've got an extra powered sub woofer and I've got a newbie question. Can I hook up my two sub-woofers in parallel so the one signal from my receiver drives both? Should I - does having the second sub-woofer buy me anything in sound quality? FYI, I can separate one sub-woofer toward the front of my room and place the second near the back. FYI, my room is octagonal shaped and it measures 19' from flat wall to t flat wall. Thanks.