I have a current generation Time Capsule in my upstairs office, along with a current generation AirPort Express extending the network down in my basement. The Express extends the Time Capsule wirelessly as I cannot (easily) run an ethernet cable between the locations. Hanging off of the Express is an 8 port switch, with 7 ethernet connections to various devices (AppleTV, Denon AVR, TiVo, etc.). Generally, the connection between the Time Capsule and the basement Express is reported as "Excellent" by the AirPort Utility, with connection speed normally above 200 and up to the max of 300 Mb/s. Would I see any benefit in replacing the Express with an AirPort Extreme with AC capability? I do have several newer devices that use AC (iPhone 6, rMBP, iPad Air 2).