When my new boat gets finished this week I will be installing my new bottomline 6500 with mag 20 dt downriggers. The question I have is how detailed is the gps charts in relation to the columbia river and tillamook bay areas. It comes standard with a world map that I don't know how detailed. Could anyone who owns a 6500 or 5300 bottomline unit give me the heads up on whether or not I should go ahead and purchase the c-map reader and cards for the northwest area?