If you ever have plans of doing Atmos or dts:x, don't get qs8's. Don't mount to ceiling either. Go onwall M2 or M3's for surrounds. Keep them ear level. Bookshelves on stands would sound even better but most people don't have the room for stands around the back.
Otherwise QS8's will do fine duty up top and sound great, I did it for years, but the second I went Atmos they were the wrong speaker in the wrong position.
Now with Atmos, the entire process of buying speakers is different, only my opinion. You no longer need two great big towers up front, and little surrounds, you ideally need the same good bookshelves or onwall speakers all around and two subs to make up for not having the larger speakers up front.
Rockstar advice...
The only thing that I would add is that most current decent receivers will do some good bass management for you, meaning that you still want "full range" speakers all around (including overheads if you want Atmos/DTS:X) but solid "bookshelf" size speakers work great. I went with on-wall M3s for my surrounds and overheads, and they work amazingly well.
That said, don't skimp on your center channel. Even with good bass management, the center channel is the most active for movies, and sometimes you need it to do a bulk of the "work" for clean and crisp front soundstage work, and leave the subs available for LFE and low bass.
