If your existing router is separate from your modem and is Ethernet only, Aerez can and should replace it as the only router on your network.
If your existing device is a modem and router combo for DSL or cable, it will still be necessary to use that device to bridge your service providers connection to a standard Ethernet format. You would then plug Aerez into that device.
In the last scenario, we're happy to help ensure you have the best connection. You'll want to disable the radio and perhaps the routing in your current device. We can assist with contacting your ISP (if necessary) to configure their modem for the best operation with Aerez.