I originally have a 5.1 setup and bought two more speakers to make it 7.1. If the movie has 7.1 soundtrack, the extra two speakers make the sound more wraparound especially in the back. It is better, but not by much. I think the 7.1 technology is not very mature yet as many people only have 5.1 setup. There aren't many movies out there that have 7.1 soundtrack. A good 5.1 soundtrack can make the movie viewing experience very satisfying.
If you are tight on budget, I suggest you wait. Otherwise it doesn't hurt to play with a 7.1 setup.
If you are tight on budget, I suggest you wait. Otherwise it doesn't hurt to play with a 7.1 setup.