Trying to figure out what unit to go with for upfront trolling motor mount. Really would like to go with side and down and 1 transducer which would be a Humminbird unit. Looking at 598-698 or 899 units. Sure would like a bigger screen but looks like 300 or more bucks to go with the 899. A Ram-mount will help bring unit up closer to see I would think?? I am guessing a split screen view on 598 or 698 would be awful small. I will take any advise I can get, thanks.