I'm planning to buy some extra speakers for the height and wide. Now, in my room, the case is that if I'd hang the height speakers, their backside will be less then 20" from the ceiling. Almost all speakers say to keep a distance of at least 20".
Same applies to my wides. Won't sound deform too much if the heights or wides are placed too close to a wall?
Possible solutions are to buy onwalls from the same series (I use B&W 683 for LCR) or sell my current speakers and buy an on wall 7.1 speaker package (Totem Tribes or Martin Logan Fresco's).
Any tips/ideas on the placement of the hight speakers?
The effect of wall proximity will be corrected when you run MultEQ, so I wouldn't worry about the 20" distance at all.