I'm not sure where you are getting the 250-300W/m2 of irradiance. The standard value used in all solar industry calulations is 1000W/m2, but in practice, you should expect to see 800W/m2 at sea level and moderate lattitude.
1000W/m2 * 0.25 => ~250W/m2.
No, no, no. Equatorial is higher because the sun is more directly overhead on average than in Kansas.