Where are you finding "Advanced Settings" under Wifi? I see options for "Notify me" and "Auto connect" and then a list of detected networks. My home wifi network has been disconnected multiple times since updating to 4.3 on Saturday. Sometimes because it was "unstable" (never saw that before update). I think it is becoming "unstable" when I get out of range (like I leave my house) but when this happens it does not automatically reconnect when I come back within range.
With this issue + this Samsung music app that keeps launching on its own, I am really regretting updating. Should have let others fight through and resolve these issues before jumping into something that was not ready for the general public.