If you're looking for something to use specifically for duck hunting, look into the hellbender double-end 10'. I love my kayak (ocean kayak trident 13) for fishing, and it would probably make a good duck boat, but for hunting I'll choose my hellbender every time. The hellbender has a flat bottom, making it a much more stable platform than the kayak. I can stand in my hellbender and pole with relative ease...I wouldn't even try that in my kayak. The hellbender also has a lower profile and is going to be easier to conceal than a kayak, and weighs less than 50lbs.
If you still decide to go with a kayak, I do recommend looking at the OK trident series...I prefer my hellbender for hunting, but I've yet to see a kayak that looked like it would make a better duck boat. There's a storage compartment called the "rod pod" on my kayak that allows me to store lots of gear inside the kayak. If I ever decide to hunt out of my 'yak, you better believe my gun and anything I don't want to lose or get wet will be in there anytime I'm en route.
**Just as a side note, you can probably find a used Gheenoe on craigslist for around the same cost as a decent kayak, and they also make great duck boats. I have one of those too...I think I have a problem.