Actually, that package for $1300 is a darn good deal for a tandem kayak including paddles. For an extra $100 you can get the carbon fiber paddles. A half pound weight difference is noticeable in a long day of paddling.
Innova makes a convertible 1 person/2 person/3 person inflatable kayak with a 595 pound weight limit for $750, and Aquaglide has a tandem model rated at 600 pounds for $800. Both has the conventional tubular structure floor which is not as rigid as the drop-stitched design, though the Aquaglide Klikitat is a high-pressure model that might be a reasonable option. Consider that once you bought paddles and other accessories (that are included in the Sea Eagle package), you would be back up to over $1000 anyway.
The higher the buoyancy/weight limit of the boat, the better it will track for you. The closer your combined weight gets to the limit, the deeper the boat will ride in the water, affecting performance.
If you want to explore other options, AirKayaks (for which I am including the links below for the two other models I mentioned) is a good company (though they don’t stock Sea Eagle) and you might consider calling them for advice on models they might have for your usage and cargo capacity concerns. I have bought from them several times – they often have good deals on demo boats and factory blems of carbon paddles.