Can you save me some money?

[usngsm2]

I have an lowrance X135 on on the bow and its black and white. I have the Lowrance 522c igps on a ram mount on the driver console. What I would like to do is put the b/w unit in the console as it was originally and get a color unit in the bow. I am not sure if I should get another 522 or a better one? I was thinking that the best unit should be on the bow but after looking on the lowrance website I am lost. I don't know the difference between a dual signal and single. I am lost as to features in these units that I need and don't need and power. I have been web surfing to try to learn more but there is limited info out there. Any suggestions ?