There`s an article in premier issue of Stereophile Ultimate AV (former Stereophile`s guide to home theater) - 5.1 or 7.1:How many channels do you need? Hope that will help. I personally prefer and use 7.1 now(had 5.1 before) and I like it.
7 or 5 speakers
HT room dimensions are 14 by 22. I am seated about 16 feet from the screen. Should I use a 7 speaker setup with side speakewrs or is the 5 speaker setup good enough. What information is processed by the side speakers that I might miss? Also.... 12 inch Velodyne sub enough to pressurize the romm (I don't listen to rap, dance or any crap and it would ONLY be used in movie applications, not 2 channel).