If it's a placebo like Palmfish seems to be suggesting, it's a pretty damn good placebo. I believe I could definitely pass a blind test between it and the STX but I know that doesn't really hold any validity. I'm a bit of a skeptic when it comes to this sort of thing so I wasn't really expecting much but I'm loving it.
Not even in the slightest, the 400 like the HD650 are pretty pleasing and non harsh to listen to, plus open headphones are great. I love the denons to death, but the do resonate inside those cups. 400 sounds very natural at least in the presentation of the sound.