I currently have a Denon Av10SE amp, Mission 753 fronts, 751 rears and 75c1 centre. REL Stadium sub. I am looking to add the Denon POA 2 channel power amp and change the 751 rears for something else (needs to be wall mounted). My questions are - 1/ for 5.1 would I be best using, say , Mission 77ds speakers for the rear? 2/ If I went for 6.1 could I use just another 77ds (yes I know they only sell them in pairs) for the rear centre, or would another centre (such as using the Mission 77c1) be better? 3/ Can someone explain 7.1? thanks for any help.