I actually got a Seasonic Super Tornado 300 and it doesn't fit quite right.
Problem is that the X-Qpack has a flange of metal in the lower left corner of the back of the case that interferes with where the power plug inlet is (plug plugs in ok; it's just that the plastic socket edge inteferees with that extra flange of metal on the X-Qpack. Nothing that some tin snips can't take care of, though. Just not plug and play, I guess.