Well there is many good names in fish finders some of them are lowrance hummingbird and eagle which is made by lowrance. So if your budget is 400 dollars i would look into getting a sight immaging sonar fish finder. Like a Lowrance x135Power pro sonar fishfinder or a lowrance x510c full sized color sonar fishfinder also an eagle fishmark 500c color sonar fishfinder.
I hope this helps but like i said lowrance is the best but eagle is made by lowrance so they are also very good and so is hummingbird.
So good luck on the purchase.