May or May not be of any help, but I have an Onkyo SR804 reciever with a sunfire subwoofer and have found that I have to really turn up the Onkyos subwoofer output to get anything out of the sunfire. My procedure was to set the recievers subwoofer output to 0Db and set the sunfire subwoofer to 0Db for calibration. I found that I barley got any output with this configuration and turning up the subwoofer to full output (+15Db) would produce very little bass, however I found that if I turned up the recievers sub-woofer output to +10db and left the sunfire at 0db I would get a pretty decent output and setting the sunfire up by 6db it would rattle the rafters and shake the walls just fine. I beleive the onkyo recivers has a lower output than a lot of recievers. The bass from my subwoofer is clean with no signs of distortion so I just didnt worry about it, however playing around with the Onkyo I found out that if you go back to the factory defaults on the 804 it will default the sub-woofer output to +12db and the other speakers are defaulted to +10db.