I don't believe that's true. To size a pump, you first decide what turnover you want to have for the tank, and then get 2 pumps that each provide half that flow rate. I like to have 2 pumps in the sump, submersible pumps because they're quieter.
So, like Takagari said, you want to have around 3000 GPH pump output. Divide that by 2, you want 2 1500 GPH pumps. Then figure you'll have 5 feet of head height (sump on the floor, directly under the tank, tank is 30 inches high, stand is 30 inches high), and you'll have 2-3 90's in the run of return pipe, you'll be lucky to get 2000 GPH delivered to the display tank.
So.....buy a pair of Laguna MaxFlo 2400's.
Now....about K1 Media....are you really sure you need that? Talk to the Stingray guys in that forum, ask them if they think K1 is absolutely necessary. Or can you get away with Rays and Arowana with just bags of Matrix in the sump.
I know K1 is what all the cool kids are doing these days, but it's expensive, and takes some planning and trial and error to get the right turnover of the media with the air pump? I think? And if there's a big air pump involved, it's gonna be noisy, too. I don't like noisy tanks.