Victor, welcome. As Eric pointed out, the bookshelves have the more precise imaging and are better for the front speakers, while the QSs give more of the spaciousness that's good for surround sound.
If you're going to place the QSs on stands, they should be spread as widely as possible, since they're side surrounds, probably almost up against the side walls. Since there won't be any 7.1 back speakers, it's a good idea to position the side surrounds a little bit(maybe 2')farther back than directly to the side of your listening position, to lend a little "phantom" back imaging.
