I think you would be better served with a combo DF/GPS instead of a separate GPS. To me it is just easier to work right there on the DF screen when you see something you want to mark on the DF just hit the waypoint button and you got it.
Both HB and Lowrance make good units. I would suggest that you call Brain at BBG Marine, one of our sponsors, and tell him what you want and your budget. He usually beats the box store prices (Cabelas, BPS etc) and may have a close out on some units that will get you a much better unit for your money than you other wise would have gotten. He ships really fast too, I think I had my DF about 3 days after I talked with him.
Mark 1:17 ...I will make you fishers of men