If you Google : Cab-SB-28 or 29 ;

Adjustable Satellite Speaker Wall Mount (Max 7.7 Lbs/3.5kgs)

For ceiling , I don’t know.

It seems that I do not understand what the 900$  aforementioned refers to .

Thanks!  I will definitely pick you a center.  The will give me 2 fronts, center and I was got to put the Elac book shelves at the ceilings, about 8 feet above the towers. pointing downward toward the Soundstage.  I would be able to get a really good sound from them as I can connect quality cables to it.  I will get a transmitter when I add the rears to minimize wires to rears.  

Listen to a Marantz

Home  theater essentiel and low budget  : Sony HT-A9 

Don't forget the center speaker.  And you may want side surrounds and rear surrounds.  then there are the atmos speakers.  That gets you to a 9.x system.   I am shopping in about the $3k range and I'm interested in what people have to say in response to your question.

Jerry