I don't think it can hurt to have the fitting done if you can afford the money. It used to be easy, because we all followed the same rules of thumb, and all the bikes had basically the same points of reference. It's very different now. However, if you do get the fitting, I would highly recommend doing it on a saddle you're actually going to use. Otherwise, your fitting might be useless... since you will sit differently on any saddle you get, and that alone can affect the most important aspects of the fitting.