I just bought an Onkyo tx-sr501 and i was testing out the power. I have a KLH subwoofer (E10) that i got from costco for 80 bucks. I noticed that once the volume got past a certain level the subwoofer does not seem to get any louder. Is this just because it is a crappy subwoofer? Do most people have separate amps for the subwoofers? I didn't try moving my sub to a different place but i did aim it different ways and it still couldn't get louder. Could this be a location issue of should i just consider buying a new sub. Im pretty sure that costco will take back the subwoofer (i saved the receipt just in case). Does anybody know if this is true?