I have an 859ci hd unit that I need to replace the transducer on and am confused to whether this unit has down imaging. When I went to order a replacement they said I needed the di transducer but that unit would say down imaging on it would it not? My unit just has 859cu HD sonar gps. The transducer that I currently have is xnt 9 20 T and worked fine. I am thoroughly confused now as to which transducer to purchase.