I've never heard a system like the one you've described. I can tell you the two side QS10s add a lot to music in PLII and Neo at lower volumes. If I turn the system up to reference, the sides are not required and stereo gives me almost 180 degree coverage. Perhaps in a different room, the actives wouldn't need help from surrounds even at lower volumes.
For movies, the actives alone can't cut it no matter the volume. Surrounds have their own content which the actives alone can't replicate.
There is a clarity and immediacy to the actives that no passive I've heard can match. With passives, there wasn't much difference between an M3 and an M100 for movie watching. The actives blew that paradigm out of the water.
