I suppose 6.1 really would be the easiest if you wanted to expand the surrounds, though, personally, I'd probably stick with 5.1 in that space and put the money toward the second sub and/or amp that you're considering. If you did do a rear surround or surrounds, however, you'd have a little more space between your couch and the speakers than I currently have. I only have around 2 feet. While not ideal, it does work.

Also, the pictures of the family here and on Facebook are always good to see.