I have a Helix 9 Gen 2. I Like it...........
The side imaging transducer that comes with it, is not as good with the Down Imaging side of the fence as a standard Down Imaging HD transducer.
If you ONLY plan on using down imaging, I'd get the HD Down Image transducer.......if you plan on using both down and side from the same unit, I'd almost get a splitter, and go that route............
Later,
Geo