I agree with having two seperate units. Just in case you have a failure with one. I personally have a Garmin 160 blue, and a Garmin 176C. The great thing about garmin is that they interface with each other. When you mark a loction on the water on your GPS, it will also tell you how deep you are at that time. The GPS will also interface you with most new VHF radios, so if you need to send a may-day all you have to do is hold the panic button and your location is automatically sent to the Coast Guard. Something to think about!