Adding speakers in theater always seems like the cheap way to enhance the experience. I've always gotten more out of quality than quantity, here, you might say.
While some movies are a little off-beat on their presentation of 2 channel, I love watching a movie at my fathers place. I gave him a 1543 Peter Daniel's DAC that his DVD player feeds into, and some Hawthorn Silver Iris speakers modified with Obbligato Golds and deadened. They're on top of some musical low playing large subwoofers (efficient) and there's an old 15in Adire Tempest for real low notes. (unfortunately the neighbor isn't a fan). He doesn't give two shits about the fact that he's not using all 7 channels on his receiver. This is making me want to go watch The Expendables at his place again... Once in awhile the voices in the center could be stronger, but the music sound track, explosions, gun shots, etc, are very engaging. It's better than the big screen (well that I've been too). Ironically he still has an older 200+lb Sony CRT. Nice picture, awfully small in widescreen.