Best answer by AjTrek1
If by extra Amp you mean a Sonos Amp or Sonos Connect: Amp you could connect the tower speakers to either to send Sonos to them.
If by extra Amp you mean a spare AVR you can connect the tower speakers to it and incorporate a Sonos Connect to an AUX input to send Sonos to them.
You could also incorporate a Sonos Connect with the existing Denon AVR-X4300H if it has an unused AUX input. The sound would be auto directed to the main L/R speakers (in stereo) as there would be no center or surround material being sent.