I'm looking to buy a new finder for the front of my boat for around $300. I have a Humminbird 798 on the console and would like to stick with Humminbird if possible. Any comments would be appreciated.

One that has a screen big enough that you can see all that you need from a standing position.

I just put a HB 570 DI up front and am really pleased with it. Mounted xdcr to trolling motor. Runs about $300.

Is the down image very readable in the sun being grey scale.

It is readable, just wish the screen was larger, that would definitely help. The white background is very readable. I like the dual screen mode though, white background/black background, but it does get difficult to read when I have that selected.

I run a HB 383 on the bow. It is plenty to stay on the fish after you have found them with your larger unit.