That's probably one of the nicest MS Paint pictures I've ever seen! Really.
Looks like a great setup. I have the same problem as you with the couch being up against the back wall. For this reason, I had to drop my plans for a 7.1 setup and go with a 5.1. The reasoning is that the two rear center channels wouldn't be far enough away from the listening position to create a proper soundstage. I didn't consider 6.1, but I might. Not sure if there's a similar concern with 6.1. Time to head over to Google and see what I can find, I suppose.
Ken.
