A:Answer Hi, and thank you for your question. It really depends on what you want to do.
You could do Arc + Sub + One SLs as rears or Arc + Sub + Amp + In ceilings (powered by the Amp) or x2 Amps + Sub + 2 Pairs of architectural speakers plus many more options. As long as you have Arc, Beam, or Amp plugged into the tv as the "front" channels, you can decide what you prefer to use as "rears"