How can I upgrade my router from XB3 to XB7

I currently have the Performance Select Internet Plan and the XB3 (DPC3941T) router. I would like to upgrade to a more modern router; one that has VLAN support so I create sub networks. I need a router that has both 2.4 and 5GHz and I need the router to have a minimum of 4 ethernet ports. It looks like the XB7 would satisfy my needs. The page to customize internet equipment doesn't allow you to specify which model number you want. It only shows that you can add an "xFI Gateway" and says nothing about which one. What do I have to do to get an upgrade to a XB7?