I have 2002 vintage Raytheon RC 530 chart plotter with "C net" navigation chip. Have Lake Michigan chip which is cool but not of use. Where to sell this? Am looking for chip for Upper Miss River as boat is on Lake Pepin with good depth map. Any experience with upper Miss river charts? Can one view these B/4 plunking down $200 for these? Also have Garmin gps 76cs - any experience with their chips for upper Miss river with depth chart? Cost for Garmin map is half of the chip for RC530 chip. Thanks.