If you go to SI, the larger the screen the better. If you are shooting a beam out 70' to each side of your boat, that is 140' on your screen. Imagine the size of a bass from 70' and you can see why a larger screen is preferred. Finding structure is much easier but still larger is better.

For me order of importance is Side Imaging, Down imaging then Chirp. Maps are more important than plotting to me especially if you fish multiple lakes.
Yes Down imaging works well at 12' and less.
There are some factors involved in the transducer. My last boat wasn't all that fast and the way the SI transducer was mounted, I did not need another transducer mounted inside the boat. Generally speaking though, yes you will need a 2D transducer mounted inside to get high speed readings. I don't use one as I am not searching for fish at high speeds and from underwater dangers, it would only tell me what I had just hit. I rely on map cards and knowing when it is time to idle.

Right now Humminbird Mega units are the best SI on the market. Garmin just released new technology in some of their units that is close to watching a tv screen and seeing the activity in the water while fishing. IMO Lowrance has the best 2D and DI. You would have to research each brand as some of them don't come with everything in the box and you will have to add things to get the best stuff out there. Humminbird for example has everything for their unit in the box with the exception of needing to do a trade in on the transducer for a trolling motor mounted one.

Another consideration is your trolling motor. If you ever want to get one that links to your fish finder then that is a consideration that you would have to consider.

I'm considering upgrades to graphs in the 5" to 7" range.

In order of importance for casual Bass fishing mostly in 12 ft or less, how do you rate Chirp, Down Scan, Side Imaging?

Which is more important, Plotting or maps?

Is Down Scan very useful on the Bow in 12ft or less?

Is it necessary to have 2 Transducers with Side Imaging in order to get depth readings on plane?



What new products and features are coming out with new models?[color:#FF0000][/color]

If it has GPS and mapping then you will get a colored screen of a map showing you your location, waypoints and tracks. If you google navionics web app you will get a working map that is the same as a navionics card. You can see everything that would show on your lake minus your own trails and waypoints. I'm not familiar with Lowrance but I believe that is a popular unit.

Consider linking the two units together if that is an option that way they can share waypoints