Normally, for 5.1 you want the Q's to be to the sides of the listening area. Slightly back/front of your ears is best. Rear speakers are normally not intended to be used for surrounds, but some people have no options.
If you can't place them on stands or wall/ceiling mount them, you may not have any other option.
I have 4 Qs8's, and they work great for music as well as HT, in my opinion. Direct radiating speakers (bookshelf) will not envelope you in the experience as well, but still should to fine.
