In a recent issue of Sound and Vision they had a small article on set up. The diagram with the article was a good look at the acceptable setup. The side speakers can range from 90 to 110 degrees. This works better for me as I can not get to 90 degrees as it would block an egress from the room. I have my back speakers about 150 and the front about 30 degress. I try to keep the back and side distances from the main listening positions about the same and both are closer than the front and center. I use Full Range Meadowlark Speakers for the 5 speaker positions as I listen to a lot of SACD recordings and wanted the closest match to my Shearwater Hot Rods for the front Audio system (seperate amp and preamp connected to HT with a preamp bypass). As far as the 6th and 7th, I just have a pair of small Infintys that I can hang from the wall. As far as telling a big difference, I listened in EX to Monster's Inc. and Gladiator and thought it made a huge difference in several scenes. The back Speakers really filled in gaps. I only use the 5 channels on 5.1 movies but I do use the 7 set up on Pro Logic 2. I cannot say that it makes a great difference one way or the other in my room and I am glad I kept the expense down on the back speakers.