If you Knoxville area guys want to check out the old Humminbird units maybe we can arrange a day on Douglas when the weather gets better. It's easier to get the big picture when you're looking at it. Side image is hard to understand for most people until they can look at the lay of the bank and then ride over it. I'm free Friday after 1:00 and pretty much any Saturday or Sunday.
One of my fishing partners uses Lowrance. Might can get him out to see both.
Now if you want to get a little deeper, Brandon does guide trips and will do sonar only lessons on the lake also. I'm not sure what he charges. He's excellent with Lowrance units.