If I understand your question properly, no.

The Sonos soundbar, in all its models, contains the front right, center and left channels. There is no way to separate them out.

The Sonos Amp allows you to set up third party pairs, but not Sonos Fives, as front right and left, with a simulated center channel.

On the other hand, if you’re using the Fives as a stereo pair in a ‘room’, without trying to use them as home theater speakers, you certainly can add a Sub to that ‘room’, and the Fives will hand off the lower frequencies to the Sub. 

Oh, you can never have two mini-subs in a single room, either. You can only have two full size Subs as part of a home theater setup, and not part of a standard Sonos ‘room’.