Go for as big as screen as you can afford. If you can find a used 898 or 998 that might be the way to go. They tell me that the new 899 dosent have the larger transducer but I had a 798 with the smaller transducer and it seemed to work ok. With the larger screen you can see things so much better. My personal opinion is nothing smaller than a 998 for Si. I think you can get by smaller with DI as you are just looking straight down instead of trying to find something 100 feet away and tell what it is.