I went for the Song Surround 1 for left and right surrounds wall mounted on swivels, and Jim did a custom sized box WOW1's wall mounted on French cleats for rear duty. This also allows us to select the rear speakers and surrounds for pool table/ping pong area as well.
With some spare multi-channel amp capacity, I pulled my old M&K SX-4's into duty as wide speakers. For movies, the receiver expands out the sound very well.
For most use, movie surround content isn't too picky, and you could certainly experiment. Main thing I've loved on the Salk's is the clarity of the surround content- footsteps, birds, etc sound very very good and frequently surprise people. ("Hey, is that our dog barking?")