Best answer by Airgetlam
Sonos doesn't work that way. The "base", as you put it, is actually 3 speakers, Front Left, Front Center, and Front Right. So you wouldn't need the two PLAY:5s that you indicated as front speakers.
So, in your scenario (which matches two setups in my home), you'd have a soundbar (PLAYBAR, PLAYBASE, or Beam), a SUB, and two PLAY:1s as surround speakers.