I recently bought a Harman Kardon AVR-630 refurbished off Harman Kardon direct on ebay. I had heard decent enough things about them and honestly the receiver seems to work pretty well so far. With one exception: I'm not getting much for sub 100hz frequencies. I don't have actual equipment to measure it, I'm just generalizing here. I have it hooked up to 5 15" Selenium 15CO1P coaxial speakers in their recommended boxes - these bad boys: I'm wondering if it's possible that they're just too much for the receiver to push? I really doubt that's the case, especially since I had them hooked up to my old Sony receiver and it did great. Is this natural for this receiver? Is it just meant to be used with subwoofers? I have it set to no subwoofer so it's not that, but it is my first HK so there very well could be another setting I'm missing here. Anyone have any ideas? Thanks if you can help..