For about $300 I would buy this fishfinder from cabela's. It has GPS built in and you can add the navionics chips to it which are an invaluable tool for fishing.

http://www.cabelas.com/cabelas/en/templates/product/standard-item.jsp?_DARGS=/cabelas/en/common/catalog/item-link.jsp_A&_DAV=MainCatcat21404-cat601663-cat21448&id=0075168020954a&navCount=1&podId=0075168&parentId=cat21448&masterpathid=&navAction=push&catalogCode=9IS&rid=&parentType=index&indexId=cat601233&hasJS=true

My 2 cents!

-John