Q: Airport Express and Cisco E1000 router?

You can effectively extend the Cisco's wireless network by creating a roaming network with both routers. Note that this would require that both routers be interconnected by Ethernet. Since the Express will perform a new role, be sure to perform a "factory default" reset on it so that it will be in its "out-of-the-box" configuration.

THe Time Capsule is just an example in the document. Other Apple routers like the AirPort Extreme and AirPort Express operate exactly the same way.