I also am thinking of adding a Terrova to my boat but will be putting a quick release mount so I can go back and forth to my cable steer when dipping in the summer. On the DI unit you need to go along with someone with one and see if it's something you will like. Or in better words "if it's worth the extra $$$". I have a 1159 up front with DI and very rarely fish fast enough to make it preform the way it should. I run a split screen with DI and 2D but usually don't get a clear image because I am in shallow water and not going fast enough. If you fish deeper water or troll pretty fast it can help you find stuff and have a clear image of what is really down there.