I keep two gps / chart plotters on board. I use a handheld Garmin unit as an emergency backup and for the dingy. I find the small screen very difficult to navigate with but it serves its intended purpose. Don't get me wrong, they are great little units but I much prefer the larger screen of the dedicated chart plotter as the primary navigation aid. Hand held units are soooo portable they are a no brainer if you want to use it on more than one boat. The dedicated chart plotters will have all the bells and whistles you want and then some. You can pick up a previously used, high end unit on eBay for very attractive prices. I highly recommend the Raymarine units. I've had them on a few boats over the past 20 plus years and have never had a problem with any of them. The monochrome RL70RC or possibly the color version RL70CRC will be in your price range but you'll have to add the cost of an external antenna to those systems.