My first thought is to check your bass management setting, specifically the large/small settings on your QS8's. If you have them set to large, set them to small with a 80hz or 90hz crossover point. Having them set to large could surely stress the woofers and perhaps blow them if you are watching movies at close to reference level. You are also wasting a bit of amp power as any content sent to the surrounds below 80hz could be amplified by the subwoofer.
If it's the receiver that is clipping badly, it's the tweeters that will generally get fried.
