Hi Bassman,
Ideally, for a 5.1 configuration, the surround speakers should be mounted on the side walls not the rear one. As Alan has mentioned before movie soundtracks are mixed with surround speakers on the side not the rear.
When a couch is against the back wall, it should be pulled away from it as much as possible (a few inches will help), absorbing material should be installed behind the listeners' head. Finally, the surround speakers should be mounted on the side walls 12 inches away from the back wall. When not possible, because they are very placement forgiving, the Axiom surround speakers will also give a great performance on the backwall. Then they should be installed on each side and a few feet away from the couch (when possible), one foot or two feet above the seated listeners' ear level and, 12 inches away from the side walls.
For a 5.1 configuration system powered by a 7.1 A/V receiver, even if the surround speakers are installed on the backwall they should be powered from the side surround binding posts of your receiver not the rear ones.
