I just purchased this gps/fishfinder. I would like to get a mmc/sd card for this unit, either a hot spots, or navionics. Does anyone have a prefrence on which is better, and are they as great as the websites make them out to be. I do fish a lot of deep cover, and I am hoping that the map would help me find some spots that are not so odvious to everyone else. Thanks for any help you can give me.