Looking to run two helix 9 units at the console of my Ranger. I would obviously want si on one of the units. So the helix 9 si mega is one of my choices. Wondering if I can run a standard 2d sonar gps combo as the other unit and run that unit off the si transducer and have si on both units. Does the si come strictly from the transducer or is something different in the unit itself.