wca-411

Hi fellas! I need some help here. I've a WCA-411 8ohm cabinet (and a 400W amp). I want a power upgrade. So if I add a WCA-211 8ohm cab what do I get? if I'm right: 4x10,8ohm,600W + 210,8ohm,300W= 4ohm, 900W Correct me if it's not like this. Thanks