If you want to maintain separate music in each “zone”, then you’d need a Sonos Amp for each pair.

If you want to feed the same input to all six “zones”, then you’d need a replacement amp with 6 zones connected to a Sonos Port, which would feed the signal to the purchased Amp.

Depending on the speakers, you  can likely get away with two “zones” per Sonos Amp,  but they would both be playing the same thing (there is one set of speaker terminals per Sonos Amp).