I have to say that of the brands, I think lowrance/simrad have some of the better plug-and-play stuff. At least across the HDS line. You can network units together and your latest unit will impart its abilitys to the older units, and you can add on the same AP and radar across several generations of HDS, and they are attractively priced. granted, they have had some premature releases, but it's pretty cross compatible.