Drew - the Elite 4 DSI is down-imaging only. It does not have regular sonar.

frnklwrnr - I think you will be hard pressed to get imaging capabilities for extreme depth. The tech is just not there really especially at Elite 4 costs. You need the lower freq ducers for extreme depths(50 or 83Hz). All the imaging stuff is higher frequency and has limits.

At this price point, I personally would go for GPS and the strongest 2d sonar you can get. The fish show up as dots with DI instead of possibles arches for regular sonar. The DI will help distinguish the structure on the bottom a little better but it kind of sucks at pointing out fish. My opinion. I rarely fish straight down so SI has more worth in my book vs DI. With that being said, the lower price / small screen units typically have less power and don't produce the awesome Side/Down imaging stuff you see from the $$ units. My advice is get the biggest screen size you can afford. No shame in buying used either. Check the for sale area on some of the larger fishing sites like bassboatcentral. Everybody has been spending their rebate checks on newer stuff and dumping their older units. Nothing beats time on the water though. This guy that float tubes with me(while i yak) knows the bottom of the lake better than most fishfinders just from time spent.

I find the GPS extremely valuable for finding my crab traps and getting back onto hot spot. If you don't have separate GPS, get one on your FF.

I currently have and use a humminbird 597hd di. I've had it a few years now. The di is an attractive feature, but I've found that it is only really useful in shallower depths. The detail fades with depth. After 50-60ft, it has to be a big structure for you to see any real detail. You'll probably see a tree or something like that if your in fresh water. But, anything around 100ft or deeper and the regular sonar is going to be better. If I were to do it again, I wouldn't get it. The regular sonar and gps features are way more useful.

I have the same unit. I love that thing, but my previous sonar was 20 years old so the upgrade was tremendous. I find the DI has proven to be helpful down to 150' (deepest I have tried). I can see boulders on the river bottom and distinguish bouldery bottoms from bed rock and things like that. Detail is certainly better in shallower water, but I have found that the DI provides a lot more detail than 2D at any depth.

I agree that DI is not there to mark fish. I would definitely get it again, but I would definitely not buy a DI only unit.

The view I use the most is the DI/2D split screen. When returning to previous spots I use the split GPS/2D. When trying really hard to see fish or watch my lure I switch to 2D only mode or split zoomed in 2D mode. I almost never run in DI only mode. I think that the DI provides a lot more information about what I am looking at.

Here is an example. Many times if you are passing over multiple trees with a several branches each, on the 2-D sonar some of the branches look like fish arches (because the enter and leave the cone without you ever seeing the tree to which they are attached). With the wider DI view I can see that instead of fish it is just tree branches connected to a tree that is out of the 2D cone (this is the only time I switch to DI only mode). If the tree shapes "match" on the 2D and DI views and I see arches I look hard for dots on the DI screen. I know I am definitely seeing fish then.

FYI, on the HB support page they list the DI as being good to 350' and the 2D sonar being good to 600'. That is for freshwater. I am not sure what the equivalent is for saltwater. That is more than good enough for me.

CY, If you are losing resolution on your DI maybe you either have a bad transducer (not completely broken but not operating efficiently), imperfect transducer install (tilted a fair bit or some air bubbles if in the hull) or perhaps your settings are not optimized (you may have done this, but I figured I would toss it out there).