For larger rooms here is what a 7.1 setup would look like. If your sitting in that back couch, I would just start with 2 Qs8's for a 5.1 setup and either place them on the ledge behind the couch spread out as far as possible. You could even angle them in slightly if you wanted. The Qs8's are very forgiving in placement and sound good about wherever you put them...
Something tells me once you get your speakers, you will have lots of questions on calibrating them with your receiver.
Not to worry, we are here for you...