I just got a denon 3803 and wondereing about the speaker placement on the 6.1 and 7.1 setups. I currently have a 5.1 setup with the rear speakers directly behind the listening area. What would i need to add to convert to a 6.12 setup. The manual has rear speaker locations of A (to the sides of the listening area),B (behind the listening area outside of the SB speakers)and SB (surround back, On the inside of the B speakers). I'm confused. Please help. I always thought a 6.1 was an extra center rear speaker?