Ideally all of the speakers should be "full range" capable of at least 20 Hz to 20 KHz. Space and cost constraints don't permit this however so the next best thing is small sattelites and full size fronts with a sub that takes care of LFE from all channels.
As for the 7-channel stereo, the quality is not a function of the the QS8s. I had direct radiating speakers for my surrounds before the QS8s and 7-channel stereo sounded as bad then as it does now. I'm not a fan of it for serious listening because it blurs the stereo image. I use it only for background listening when I have a bunch of people over. Perhaps the problem is my very live listening environment. One day when I've corrected my room acoustics maybe I'll become a fan of simulated surround.
BTW, my QS8s sound great for multi-channel recordings
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