WIth one Amp, the same signal will be playing in the two right and two left speakers.  This is not surround sound.  With two Amps, each speaker gets its own discrete signal, with the fronts getting on-screen audio (dialog, explosions, etc), and the rears getting surround effects (ambient sounds and directional cues like a bullet whizzing by or an airplane flying over your head). 

Thanks so much. Makes complete sense. So I could add another amp later and just hook the rear ceiling speakers up to the second amp (removing it from the initial amp) once I want to spend on another if I don’t want to pony up right now? Because when streaming music it would be a decent set up.. just not surround for TV.. or am I missing something about music?

That would be correct.

Want to make sure I get this right and understand… so would the second amp speak wirelessly to the first amp when the TV is on to be the rear surround speakers? Since the first amp would have the HDMI connection? And with music, the 4 speakers would play together since I’d set them up in the same “room” even though there would be two separate amps?

Correct.  When you set up the two Amps, the first will be connected to the TV’s HDMI-ARC connection and wired to the front speakers.  The second will be wired to the rear speakers.  After both are added to the system, you will then go into the settings for the first Amp and add the second Amp as surrounds.  Both Amps will then be in the same room, configured as fronts and surrounds. 

For music you can set the rears to be Ambient (less volume) or Full (full volume).