re: Need help with boat electronics.

I would go with 2 Elite 7's or 2 HDS 5's, or one of each... both units are $400-$500.
I never bought into the down and side scan until recently. Was fishing a local lake and lost my gopro, suction cup failed, or I mounted it on a curved surface . Regardless, borrowed a buddys boat with down and side scan, side didnt help much, but the down gave me a perfect picture of a little square, dropped a few boueys and took a swim, found it in less than one hour total. Now I knew about where it was 20-30 yrd stretch of bank but still I was impressed. Next unit will likely be a Elite 7 for the trolling motor, have an HDS 5 on the console.
To me Lowrance are the easiest to learn and operate. Ive only had Low and Birds so take that FWIW.