Interesting that most diagrams of setting up speaker placement of a 7.1 or greater system talk about angles and not so much distance... Every surround system I have seen has the farthest distance to the Main Listening Position being the Left Center Right speakers... The surrounds and back surrounds are a little closer to the Main Listening Position... Your AVR/Processor should deal with distance and levels... 5 to 10 feet, give or take, seems about right in a living room... Maybe a bit more in a dedicated Home Theatre... In my living room the surround are 6 ft from the Main Listening Position and about 7.5 feet from the surround backs which are also about 6 or 6.5 feet from the Main Listening Position...