If the current set up is working fine then just leave it alone. Set up the Hub5 in modem mode and run it that way.
Or you could just unplug you nest router and fire up the Hub5 and using it as is... see what the wifi/ethernet connections are like if you leave it in router mode and connect to the new Hub5 SSID.
Might be a faff changing a few wifi devices to the new SSID - but choosing a few key ones in distant locations should soon tell you if its ok or not. Then decide either to stick with it - or return to you previous set up.
--------------------
John
--------------------
I do not work for VM. My services: HD TV on VIP (+ Sky Sports & Movies & BT sport), x3 V6 boxes (1 wired, 1 WiFi, 1 on PA) Hub5 in modem mode with Apple Airport Extreme Router +2 Airport Express's. On 250Mbps, Talk Anytime Phone, x2 Mobile SIM only iPhones.