I purchased a new SACD (with a regular CD layer) of Beethoven's 9th Symphony by the Minnesota Orchestra (Vanska cond.), and it had me questioning the fidelity of the ATH M50. So I tried the CD with some different headphones to sort out the unusual soundstage and rather non-commercial sound, and when I went back to the M50 I realized it wasn't the headphone after all. This was one of the best lessons I've had in how the variant properties of headphones and recordings can combine in unexpected ways to trick your sense of perspectives.

That is to say, if certain properties of the headphone and the recording are complementary (one example being a slightly narrow soundstage on one of these and a somewhat wider soundstage on the other), you may accept that as normal. But if these properties are additive, they may exaggerate certain things and contribute to a sense that something is off.