I have the GPSmap 172 on my current boat. Internal antenna is ok, external is better, higher gain. The controls are pretty intuitive...sometimes I wish for a bigger screen when running split screen...I usually flip back and forth between pages. Definately get the dual freq transducer. Also be advised if you are new to GPS...if you don't use it all the time, let it sit and aquire a good constellation of satellites without moving the boat...if you are underway and haven't used it in a while, the unit will forget where it is and won't be able to reaquire. The 172C is obviously the same unit but in a color screen...are they really down below $500 for the color? Try Froogle.com for a good price...I got mine online from Boater's World with a military discount. The 172 can also be set up to facilitate DSC with your VHF if it is able, though you'll probably need a tech to hook it up. The Icom 302 is a good base VHF with DSC...a good all around com/nav package for $600 or so.