The Sundown Audio X v.3 has a bigger motor and graduates to the Zv5 coil. So also more linear Xmax. Which Means More output and less distortion and more power handling vs. the Sundown Audio X v.2 -- the X v.3 is like 85% of a Z v5 . with these upgrades; sundown audio has added 500 more watts to the power handling making it one of the most potent subwoofers in the world, that also sounds good.