You will prob want to spend 4-500 but will settle at the 6-700. You can get alot more for your money for the couple hundred in difference.
Lowrance HDS units are an excellent value. They come at a few caviots. They (Lowrance, Eagle, NorthSrar, Simrad, Hummingbird) are owned by Navico. There are so many complaints about the poor customer service, its not worth going into,.....but it's a real issue
IF you have a problem with one. Longevity may be in question because they are new this year. Software can be buggy but now that the HDS units are the new focus at Navico/Lowrance, I have seen where they actively are working the ***** out. HDS-7 (6.4" display) would be a good choice if your doing more lakes and rivers. Built in GPS antenna thats not too shabby. LOTS of xducer choices for shallower water in lakes/rivers. Including a broadband type if you want to upgrade that down the road.
For your
money, it's the one to get. Built in software too.
One thing for sure, don't get the 5". Too darn small to be very effective. Seems the older my customers are, them more the bigger displays need to be. Cheaper isn't ALWAYS the best.
I haven't been a huge Lowrance fan of late, but that opinion is changing.
Garmin units are too small. They're larger units (640 series) just had their production dates pushed back. Also, they do not have as good of a reputation for DF/FF as Lowrance. Lowrance has a heck of a leap on that and I believe THAT should be your focus. A GPS nowadays is an easier thing to create. A good DF/FF is not.
Garmin is very good too. But I would not forget how small that 5" screen is. The HDS's 6.4 is a significantly larger display, especially if you split screen the GPS and FF pages.
Just my opinion....
http://www.lowrance.com/en/Products/...-Chartplotter/