Check out the Lowrance Elite series... I have a basic Elite 5 on my tin boat.. great little machine..under $500... I've used Lowrance stuff for about 25 years and have always been happy...excellent sonar performance, and good charting.. takes all the cool chart cards... FWIW, I spent many thousands of dollars more for the Raymarine E-series setup for my saltwater boat.. other than having the networking abilities, it did'nt really show me anything very different... and it was waaay more problematic than any of the "cheap" units I've owned... If you go to the Lowrance site, you can download little emulator apps that simulate their units on your desktop.. great for practicing and getting to know the machine before you buy, or hit the water with it... Here's a shot of the Elite in action.. Yes, I'm about to get a bite
