jrmav,
The QS8 sound real good, being that I have two you don't have to worry so much about the sweet spot for the rears the sound envelopes you well, I suppose one would be Ok but I prefered the two.

Axiom M80Ti(4) Axiom VP150(1) Axiom Qs8(4) Axiom M22ti(2) Axiom M3ti(2)