HB 597 ci HD Combo Sonar/GPS.......I am lost when it comes to electronics! Is this a good unit to purchase for trolling up front? Any advice would be great as I am mentally challenged when it comes to this stuff! I am going to be spider rigging and longlining up front if that helps and need to know my speed and channel edges and such! I will be puchasing SI later for console and considering the 798c HD SI for that unit? Thanks