+1 for 60CSx.
If you plan on mounting it to the dash, you might look into the 76csx. Same features as the 60csx, but made for marine use and the layout's different. The RAM-mount for that wraps around the entire GPS instead of relying on the belt clip to secure it like the 60. If I had to do it again, I'd get the 76.
The 60's a great unit though.
If you don't have (or want to upgrade) your two-way radio, the Rino 530 has the same GPS and GPS-related features as the 60/76, but includes the two-way radio functionality. $$$, but both the GPS and radio perform well from what I've seen.