I have a Denon 3805 and KEF5005s. Now it is a 5.1 system. I want to expand it to 6.1. Also I know 7.1 is better and 3805 supoorts it. But my room is small and 6.1 is OK. My question is : Is 3805 support 6.1? Where can I put the RearCenter speaker? Same hight with rear speakers on higher? Thanks!