I have been looking at getting a new finder and have been considering the Lowrance HDS-7 or the Humminbird 797 ci SI. Both units are about the same price but you have to buy the add on structure scan for the Lowrance. I have been reading the structure scan is going to cost $600 to add on. Is the lowrance structure scan going to be worth paying 60% more? I heard that you can buy one structure scan and hook it up to two fish finders but I doubt I would buy two of them honestly. Any opinions are appreciated.