I would defo fit the sounder. A stand alone sounder has benifits over a dual purpose unit, even just as back up. I see it has dual frequency which is good for deep water wrecks. If it has a transom mount transducer, fit it at least 12 ins from prop, but not too close to the edge of the hull.
Mount it on the steering consul leaving enough room for other instriments, but clear vision so can be seen when standing near the back of the boat,
Cracking boat/outfit, saw you testing it, (well, your brother) the day you got it. Good luck for the comming season.