Northstar (formerly Navman) units like the 657 are very popular abroad. They have very nice screens, do chartplotting great, and are OK at FF. If the chartplotter is your primary function the it is a good choice.
http://www.byownerelectronics.com/st...9&cat=0&page=1
http://www.byownerelectronics.com/st...6&cat=0&page=1