Can anyone tell me the difference between the two. I have a 126sv with livescope on the bow but want to add another mount at the console with the gt54 or 56 so I can use side image while at console and move it up front when crappie fishing.

The 56 is cleaner & crisper, by quite a bit. I think it might be a tad longer too though.

Go onto Bass Boat Central and you will find info comparing the two. If I was buying one now I would get the 56 because its the latest offering. It does give you a wider side scan distance. As you probably found out its about $200 more. I have the GT54. It really delivers sharp images. People posted on the Garmin forum screen shots showing a comparison between the two. In looking at the side beside screen shots I just did not think it was worth replacing my current setup. But some of the people posted that they replaced their GT54 with the 56 and were glad with their decision. If you are looking at increasing your sidescan distance then by all means get the GT56.

I’ve had one on back order for over a month now. I didn’t know anybody had them in stock unless it came with a new unit.
JSouther I have a new GT54UHD I’d sell for $175 shipped if you go that route.