It turns up in November and I am starting to think about a plotter/fishfinder combo. My current boat has a Garmin 551S on it which seems to do the job but obviously there is a big jump in capability with the new units out there now.
November.. keep thinking and assessing.. the buy closer to the date. You will find that the current models will start to be discounted around then.. even as far as 60% of current price as the new 2019 models come out 
The lowrance/ simrad updates are not as complex as it seems, espec if your home wireless reaches the boat.. the navionics nav charts are continuously being updated...5 to 25 meg just for the nth 1/2 of the nth island .. each week.
And you can automatically sync markers, tracks , routes and other info between the unit and smart phones/ tabs and visa versa, if have the navionics app on them ($20 1st yr, about $10 there after.)
If you buy the app now, ($20) load on say a tab and the smart phone (or 2 smart phones), log in on both, you will see the maps, the sync.
Keep in mind the apps dont have all the features of the navionics gps units.
Even more basic .. is the web app just to look at.. note the contour line detail.
http://webapp.navionics.com/?ticket=ST-1493511625rNKBQNGYg0-pXbHduqG#boating@10&key=haa_F%7Dbck%60%40
Personally I prefer the Garmin gps (fortnightly open source NZ maps updates) for auto topo parcel boundaries, DoC , riding and bush tracks , huts etc. and navionics for Marine.