Powering nine home speakers

Thanks again. Can I ask what’s the risk if the impedance doesn’t match (ie using the current speaker selector and a second amp)? Harm to the equipment or just uneven sound? 

Happy thanksgiving. 

jj91709,

     I think it's important you realize something that has not been stated on this thread thus far.  Listening to music through 9 ceiling mounted speakers is the least enjoyable method I, and probably most members on this forum, can think of .
     Your audio system configuration is fine if your goal is background music but falls far short of the high quality music reproduction systems that most members here use or are striving to create.
     I'm assuming you're fairly new to this site and may not be familiar with how to configure a system so that a 3 dimensional illusion is created which credibly portrays the performers as being in the room.  
     My intention is not to demean but to convey that there are much better methods to enjoy recorded music that I believe almost all music lovers would choose once they personally experienced the difference between a background music system and a properly configured stereo system.
     The members here are generally very knowledgeable and willing to assist those with less experience and knowledge (a minimal number of 'audio snobs').  
     I'm sure you'd receive good advice either way, but I think you need to decide if just louder background music or a more involving audio system is your preference.

Tim

Thanks Tim. This is just to fill the room. I have a dedicated theater already properly configured plus a recording studio so they’re very different goals. Take care

     Okay, understood.  Then, you plan to run and listen to your music in mono, right?
     Seems like it'd be hard to perceive any of the benefits of stereo sound with 9 in-ceiling speakers.  I guess you could try by running one side of the room  as the 'left' channel and the other half or so of the speakers as 'right' channel speakers. However, I have no experience in doing this and the results are unknown to me.  For example, people would likely predominately just hear the sound from the speaker they're closest to which could be a left or right configured speaker.  So, it seems most of a scattered group of people in the room would be listening to just a right or left channel of the music and this perspective would change as they moved around within the room. 
    Off the top of my head, running all speakers in mono may be the best solution.

Tim 

Can I ask what’s the risk if the impedance doesn’t match (ie using the current speaker selector and a second amp)? Harm to the equipment or just uneven sound?

Not too many power amp can handle 2 ohms or less load, Some amp protection circuitry will lower the output or shut itself down, some will over heated and caused damage! That’s the reason for impedance protection circuitry.
If you want to use the ATM7, wire the speakers close to 8 ohms:
http://www.colomar.com/Shavano/4ps-spkr.gif