Right now I have a pair of 48" tower Definitive BP7001SC bipole speakers for surround sound, and I can tell you it sounds just like when I was using 2 StudioMonitor 450 bookshelf monopole speakers.
Surround speakers are no big deal.
Surround speakers do 2 things in movies: ambience effects and panning effects.
It does not take a whole lot to create some ambience sound behind you. It's like background music. Bose speakers can do that.
It takes some IMAGING to create the panning of sounds going from front to back, and monopoles can do a great job with that.