Fish finder / gps help

I just purchased my first bass boat. I have $500 for a new unit at the console. What would you recommend? Brand doesn't matter to me, just want reliability. I fish Erie a lot, so pretty deep water need to locate the smallies. I wa looking at a humminbird 587 combo maybe. Also, is there much of a difference between hot maps and the premium version?
Appreciate any advice.
-Justin