Garmin 620, the 400 and 500 are dead?
I have just been configuring a GPSMAP 620 for a customer and even though I am a card-carrying member of the Garmin Fan Club I was none the less amazed by the little device.
The specs and bumf don't do it justice in my opinion, the amount of extras you get with it almost make it worth a look...
Mains charger with worldwide adapters, USB Cable, Marine mount (tilt and swivel), Clip-in wiring harness that supplies power and data connections without fiddling.
The device itself is a compact touchscreen that I think makes the 451 and 551 and 556 look a tad dated, it takes G2 Vision charts and displays AIS targets.
Best of all when you put the boat to bed you simply unclip the plotter and take it home, the built in battery means you can use it in the car or plan the next day in the pub. Ideal I reckon for people who trailer launch from different sites.
Not looked into the depth possibilities yet, for which the 451S etc may well be the better choice. But even so, the king of compact chartplotters may be dead - long live the king!