3g? Ok, Get yourself the Raymarine RL70CRC, 7" Color LCD Radar and chartplotter with the 18" 4k radom and a Raystar 120 WAAS GPS reciever.
Done. Turn overlay mode on, and overlay your radar ONTO the chart disply. Best thing since sliced bread.
EDIT: OOOOPS!!! Ok, a bit mopre than 3G because you have to add a Heading sensor (a few hundred bucks) to be able to use "Overlay mode". Well worth it though. Can you say Visa?
Birdman, Capt of