What kind of TM do you have? The HB SI models provide all 3 technologies; Dual Beam, Side Imaging, and Down Imaging. If you want the latest, may want to wait until later this year and maybe use a cheaper model in the interim. The rumors are flying that there will be new models announced later this year. I would recommend talking with a board sponsor like Bryan at BBG Marine and he might be able to provide some insight on availability or possible upcoming changes. For the bow, I would not recommend anything less than a 9 or 10" model....bigger is better for older eyes...LOL