The thing about the sound volume maybe even greater using AC6000s. There was a release of the AC6000 that had one of the loudest sound sets I have seen. There were other engines that had very soft sound sets. If I put the narrow nose -8 sound set up front with an AC6000 PS2 trailing, it's hard to hear the horn on the lead unit.
So I could not blame that on the WIFI alone. Unless you don't have this issue with the remote?