So my girl is starting to learn how to ride so looking at these so I'm always right there with her. Looking at the x1 slim. Now if I buy one for my bike does she have to buy another for hers or do both headsets run off of one box? Can you buy extra headsets without having to buy another box? How well do these work? How well can you hear and talk to each other? Was it worth the $400 they are asking?