I think the manufacturers do a great job of building units for just about every market that is out there. From someone that simply wants a unit to find depth, water tempurature, and show fish, to a step up unit with downscan imaging. They do a pretty good job now days of having units that are for everyone.
I recommend a couple of different options. The first thing I would do is to head to one of the bigger box stores and play with the units. This will give you a good inidication of what is "too much" or "not enough" for what you are looking for. The only unfortunate thing about this is that the majority of these stores simply cannot have a model of every unit on the show room floor at one time. It would be impossible. Another consideration is that many of these box stores do not have an employee that actually works the department. Many of the people that are working there are factory reps. So, if you find that they are trying to steer you in one direction, keep that in mind. ON the flip side, they usually know about everything there is to know about that particular product line.
I would contact Brian over at BBG marine. He is very good about knowing what he has, how it works, and how it would work for you. Once he tells you about it, you can research it online or find out of a local store has one on demo that you can look at. I've had really good luck with the simple Garmin units over the years. They were very easy to use, very few buttons, and did exactly what I needed it to do. Tell me depth, tell me tempurature, and mark fish arcs on the screen.
I own all lowrance units now and have little experience with the smaller type units you are looking for so I would be of little help in that regard.