Bruce, it's good that you've been pondering this decision for about two years now, since it deserves full consideration. If your setup is going to be 5.1, without back surrounds, it's suggested that you get QSs for the side surrounds. Their very wide dispersion gives what most consider to be a better surround effect overall, although some decide to combine these with direct radiating back surrounds, for a little more specific localization there. Aiming direct radiating side surrounds to bounce most of the sound off of the back wall is another option to increase the dispersal of sound.
