Just got a Extreme AC to replace my Extreme N. In setup it has a Wireless Options button (don't remember this before) that has a a 5 GHz option. It creates another WiFi with 5 GHz added on the end (so you have 2 WiFi). I checked this and connected this way. I had much lower speeds to my AirPort Express connecting to this WiFi. I thought 2.4/5GHz switching was auto and didn't need to be selected. Is this a new setup to the AC? I basically understand that higher frequencies can carry more data but have a more limited range. What is the beast way to setup and use?