I bought a deck boat that I plan to use as a fish and ski for the family. I've been looking into Fishfinders with GPS and from what I've read SI and Chirp are the way to go. Ideally, I only want to spend around 450, but I'm willing to spend a little more if that's what is best. I've found decent 5" models in my price range, but some people recommend 7" or larger which adds a couple hundred more onto the price. Anyone have recommendations?