I recently took a lightning hit near my boat. I believe this is why some of the electronics on the boat are messed up. Insurance deductable as much as the damage, so I'm not making a claim. I have a NAVMAN 5500 5 inch. Was looking at the Garmin gpsmap 541 or 546. Both the same unit except the 546 is $150 more for a higher resolution screen. The 541 is already better than the unit it is replacing. Which one to get? Or if you had different thoughts or suggestions. The unit is mounted in the dash so the rear is not exposed. It also needs to fit in the existing openong, so it needs to be square, not rectangular.