I also have a small room, but when I expanded from 5.1 to 7.1 channels I found it to be a significant improvement. IMHO, 7.1 is so much better that I would never go back to 5.1. The sound is more enveloping, surround effects have more front-to-back and side-to-side depth, I feel like I'm in a larger room, and I do not hear any DSP artifacts. The challenge is synthesizing the extra channels. I use Lexicon's Logic 7.
Bruce
Bruce