Dipole/bipole or direct radiating

I have a 27'x 16' room that will be pretty much dedicated for music and movies. I have heard a lot about what kind of speakers to put for surrounds (some say direct radiating other dipole / bipole). I have Revel Salons and Voice but I am unsure if I should get the M20's or the S30's / Embraces for the back. Any and all comments are welcome.

Thanks