Elite4 DSI is in the low range as far as price, has great GPS and downscan. If there's a hard figure that you're looking to spend, that might be a good place to start.

IF you just want a unit that's cheap and uses 2d sonar, I'd get the cheapest possible. IF you want GPS, then I'd look a little closer. IF you want DI/GPS, that's another scenario entirely. 2D and DI couldn't be more different in what shows up on the screen, and how you identify what you are looking for. I have cedars that are right next to other underwater structure, DI makes is really fast and easy to find and fish them. 2D, not so much.