Since both the Cisco device and the Arris device have only one Ethernet port, I see no way to add other Ethernet devices to that location without a switch.
Also note that your switch needs to support IGMP snooping for TV to work correctly as it uses Multicast to send the IPTV signals. Not a lot of home networking equipment will support that, so you'd likely need a managed business class switch.
A decent ethernet switch will work. Don't need to spend a fortune on a switch that'll be overkill. I've got a Zyxel switch in my setup though a Netgear gigabit one would work fine also.