If you think they're heavy now, just wait until you're mounting them and have to put your faith in the bracket. Don't worry. Mine haven't fallen yet.
Funny you said that. Because I had already bought a pair of mounting brackets just like the one's I had mounted my Cambridge Soundwork surround speakers with. When I lifted the QS8 out of the box I immediately knew there was no way those guys would be up to the task! Then I saw the stock mounting brackets (had no clue those came included).