Sonar/Fishfinders

[Wishing2BFishing]

I am in the process of selecting the final upgrades for my boat purchase. One issue where I am completely lost is sonar/fishfinders . . . the only thing that I know is that I will get one on the console and one up front by the trolling motor and that I will likely purchase a Lowrance Unit. Other than that, I just don't know . . . you see, I want to get relatively good stuff with the purchase since I will be financing via the boat purchase. I don't want to turn around later and try to buy these units out-of-pocket. Also, I won't be fishing deep water. Instead, I will be primarily fishing rivers and primarily small lakes. One guy suggested the Lowrance X67c or LMS 522. I am lost . . . please help . . .