if its only for the res you dont need a top end unit. i personally use lowrance.not only do i use it on open water but its great on the ice as well. therefore you get year round use at a good price. i had issues with 1 of their units and after speaking with them sent it in for them to look at and they quickly notified me they found the problem and i had the choice to get another one or upgrade at a fraction of the cost. i upgraded and couldnt be happier. the gps units are awesome if your trolling and want to loop over a spot. theres just so many pluses.