I just saw the Raymarine Dragonfly 4DV on sale below $130. I know this is downvision only and chirp I believe. I currently have a Humminbird Helix 5 SI GPS. The downvision on this unit isn't that great and I believe it is a computer simulation and certainly not chirp. I would put this unit right next to it and use it just for downvision and put a full screen side imaging or map on the humminbird. Does anyone have the 4DV only? I can't find many screen shots online. Is it big enough to see? Is this an old discontinued model? Is it worth the price? Any other input?