id go with the elite 4 HDI version, which will give you downscan for structure AND sonar for fish.... i got one with no GPS for 200 at BPS.
This seems like a good option to me. You can get the GPS version for about $300.
I picked up the Elite-4 DSI on clearance at the end of last year. You may be able to find some of those at a very good price. (If you can live without the sonar)