Amplifi addition . . .

is there a way to utilize the Amplifi units I currently own in order to extend the xfinity wifi in my house? I just purchased an Amplifi system a few weeks ago in order to replace my old airport network. Amplifi works great but yesterday I ended up getting an updated xfinity modem which SIGNIFICANTLY strengthened my signal, however I have a couple of dead spots in the house and was hoping i could fill those with the currently installed Amplifi units without using the Amplifi router .  .  .