Hey now, us Oregon halibut fisherman have no choice but to fish deeper than 500'. For the most part, our shallower areas are pretty poor in terms of #'s of fish produced.
That said, I use a 1000 kw Airmar and a 3-4 year old Garmin sounder w/ a 10" screen on my friends boat regularly, and I am not that impressed. I think the ducer' could give fantastic target separation, but the older Garmin technology just can't display it very effectively. To really get the most out of that transducer, you need a digital sounder and a high resolution screen.