I am looking for options to enhance my boat's electronics. I have a Garmin 8610 (new to me as replacement to 7610 replaced by Garmin) and want to add a second external display so I can have full screen nav and sonar running at same time, and possibly add radar too. What devices can I get to provide the additional functionality? I am a newbie to gps electronics but am mechanical enough to install new device, wire it, etc. Thanks in advance for your input. Tom