I am in the market for a new locator and I have decided that I would like to go with a Humminbird so I can use it with my Terrova motor. I am currently going back and forth between the 899ci HD SI and the 999ci HD SI. Other than the larger screen I have heard that the 999 comes with the HDSI transducer that is capable of 800kHz. Many people have said that after the purchased the 899 that they immediately purchased the HDSI transducer separately. I am wondering if the more powerful transducer is really worth it or not. Do you really get that much better of a return? If it is then I would just go ahead and get the better unit right away.

Also, I plan on networking this unit with an 959ci HD since, from what I've been told, you can see the same thing that the SI unit can see.