Older post that went off topic a little.
It's not the QS8 clipping, it's the amp. OP said their running at 4.5 to 5 db ( assume they mean + 4.5 to +5 ) Thats well into a possible distortion and/or clipping zone.
If it helps, think of O db on your dial as the MAX volume. Anything above that (in the + ) is like overdriving the amp.
(Not really overdrive just a lack of better words....)
Here are two excellent articles:http://www.axiomaudio.com/understandingdb
To help answer the Original Posters question: Lower your loudness (volume) setting to avoid clipping or get a more powerfull amp(s) that can handle your desired loudness :-)
More info here: http://www.axiomaudio.com/aboutamplifiers