Congrats on a giant overreaction and depriving yourself of a great listening experience.
There's no point in further posts in this thread until there's an update from Sennheiser. What we know up to this point is that the 650s are definitely NOT supposed to have the same drivers and that most of us don't have hd580 stamped on our drivers. What hasn't been explained yet, and this is the only thing, is what that designation on the driver means. Maybe there was a fabrication error and a bunch of 650 drivers got marked the wrong way? I just love how 99% of the people here are jumping to the conclusion that the big-bad-Sennheiser intentionally put inferior drivers into their headphones and they were so clever as to clearly mark the drivers. Again, . Some folks need to take a deep breath and realize that this thread (and this site) are so far from the top of Sennheiser's things to do list that it might take a while to get an answer. Calm down.