answerdIf it's making distortion, the sound your probably hearing is clipping. Do you have any bass boost turned on? noI don't feel like loading the video back up. Is your box ported? yesIf so, do you have your ss filter on? i think soIt could be bottoming out a bit.
The rms on the 10w7 and the 13w7 should be the same, just the soft parts and basket should vary (basically). All that means is same motor, more cone space.