Damn! This forum never informed me about new replies. About voice, I never configured anything in my modem because there isn't any setting for it in the configuration page of the modem. It just continued working. In your case of the Syrotech modem, it should work too as you are just disabling the DHCP server and PPPoE ( ¯\(ツ)/¯ ). Tinker around until you can find something.
