I'm shopping for a GPS to put in my boat... anyone have input on a good one?

I'm looking at this one :

http://www.amazon.com/Garmin-GPSMAP-...rds=marine+gps

It seems that the standard procedure for GPS manufacturers is to sell you a unit with an inadequate 'base load' map, and then sell you a $300+ SD card with detailed information for nav & better maps.

I haven't looked around, but I'm sure there's probably hacked downloads on the interwebs for that additional stuff...