Airport use with existing wireless network.
Can I hook up my airport express and airport extreme to my existing cable modem with its own wireless router?
AirPort Express 802.11n (1st Gen)
Yes, but how you would configure would be based on what your networking goals are with them. For example, do you want to: a) Extend the range of the existing wireless gateway with the AirPorts?, b) Create a second wireless network with the AirPorts?, or c) Something else?
Will all the routers be interconnected by wire or must they all have wireless connections between them?