I did the same thing, started with a handheld which couldn't reach the nearest coast guard station, then switched to a fixed mount. One thing I would recommend is the purchase of a quality antenna. I have a Shakespeare. I have heard good things about Digital Antenna, as well. I guess the point is that a radio, first and foremost, is a piece of safety equipment. VHF is line of sight, so if range is a major factor, the higher, the better. The cost difference beteen an 8ft and 4ft is little. The same goes for an economy model vs. a premium model. Don't cheap out on the antenna.
I still keep my handheld charged up and on board as a backup. Electronic failures are not unheard of and you are not always within range of a cellular tower. While they are fun to talk to your fishing buddies on, and to listen to all the chatter sometimes, they are first a piece of safety equipment.