I am replacing my Hummingbird 300tx (Junk) with either a Garmin 240 Blue or a Lowrance X-91. They seem to fit my budget. Does anyone have experience with these units and/or recommendations. I'm leaning toward the Garmin because it looks more user friendly and has a dual frequency, temperature & speed transducer. I fish in the Chesapeake Bay in up to 100ft. I run at 30mph and need good readings of depth at that speed. (The Hummingbird goes blank). I want accurate fish readings at slower speeds in waters from 15-100 ft. Any comments??