If you mean using QS-4 for front speakers, it is definitely a not a good idea. I tried it for fun at some point, and it creates a very weird soundstage, a bit as if you were listening to a painting by Dali. For the front, you need precision in the location of objects. For the side and the rear, you need some vagueness to properly render the atmosphere. The Qs4/8 provides a good mixture of both (location + atmosphere) to be perfect for side and rear surrounds.

See Mojo's signature