Mr. Potatohead - like roar says moving from 5.1 to 7.1 is IMO very room dependent with larger rooms usually benefiting more. Additionally I also thinks it helps more if you have multiple rows of seating.
Also I’ve found that the QS8s do a great job as rear speakers especially when seating is close but the further away the back wall the more I prefer my M22s as rear speakers. Keep that in mind if your room is deep since you could upgrade to 7.1 for a lot less money by getting M22 or M2 rears. As always YMMV.
