I am currently fishing the Miss and Tenn rivers and would like to fish the Cumberland some this year. I am considering buying a Navionics 15xg map card. This card is for navagable rivers including the Tenn, Miss, Ohio, Missourri. Arkansas, and Cumberland Rivers. I have a Lowrance 525c and the background map that came on the unit is not as helpful as I'd like it to be. Does anyone have this card and if so is it worth the $200 that it costs.