(1) QS8 if you can afford them. Because, um... the bigger the better!

(2) There was a recent thread on this very topic at the AVS forum. As you see in the thread, I recommend you mount them (especially the heavier QS8's) to the stud. But some other people claim that the drywall anchors should be strong enough, which I am still unconvinced especially because you are dealing with SPEAKERS, which constantly generate vibrations. And yes, the QS surrounds come with a special brackets for wall-mounting, which I fastened into the stud using regular woodscrews. Once it is done, you simply "hung" the QS onto the bracket.

Go get a $25 stud finder at the Home Depot, if you don't have one.