If any audio setup (DAC-amp-phones/speakers) doesn't make the recording sound like I'm at a concert, if it doesn't put me there, it failed.
Setups that are called analytical never failed to fail in my book.
The PRO900 do change over time, it's no placebo. The changes are not spectacular themselves, but they do change the overall sound signature noticably. Bass gets better definition and the highs get a bit "rounder".