Dolby Atmos

1. I will be adding them as 5.1.2. Can these be substituted for 7.1 when Atmos material is not on the file/disk?

 2. I want to use these as well for music in multi channel stereo, and providing Audyssey mixes appropriately it should sound more powerful than now?

 3. I have 18' ceilings. I would assume the theaters are higher. They will be placed approximately 8' off the ground. Will I still be able to enjoy questions 1,2 relatively the same?