Advice on dinghy sounder wtd

Hi guys, im relatively new to boating and im definitely green when it comes to sounders so was chasing some advice for a sounder for my dinghy. Its a  3.4m savage jabiru. I currently have a hand held gps so i'm thinkn of going a standalone fish finder.

I mainly just go out for a crab and bream fish but would also like to look at taking it out to cockburn sound chasing crab, squid and whatever else wonders in, then once i get some more experience maybe around hillarys.

I've been searching and reading but the unit that has caught my eye at the moment is the lowrance Elite 4x with DSI. The questions i have are, is the DSI a good thing? How good is lowrance as a brand? and would anyone recommend anything different?

http://www.lowrance.com/Products/Marine/Elite-Series/Elite-4x-DSI/

The budget is pretty spot on $300 and from what i can tell the lowrance seems to be a good fit.

Any advice is appreciated

Cheers, Steve