If I were to purchase a 6.1 receiver, how effective would the rear speaker be if I were to place near the floor directly behind my couch, and have the speaker firing upwards toward the ceiling? Right now the couch is against the back wall but I can move it forward about a foot. That's not enough distance to have the speaker on the wall as it would be firing just inches diretly behind my head, so that's why I thought of this alternative placement. I can definitely live with 5.1 but I'd like to get some thought's on this though. Anyone?