It is my understanding than Sony has discontinued their excellent MDR7520 professional headphones because they can be played "too loud", according to new European guidelines.
The 7520's are very sensitive, quoted by Sony as 108 dB and a high Power Handling Capacity of 4,000mW, so yes, they will produce very high SPL indeed, but that is not obligatory, a volume control can be used! The high sensitivity, just as is the case with efficient loudspeakers, means that they can be driven to decent levels by even a small headphone amp and a larger one will be barely ticking over at normal operating levels thereby reducing distortion and improving dynamic range.
These headphones were not on sale in Sony centres, or in high street retail outlets alongside mp3 players or PC's and are not advertised to the general public, only through Sony's professional audio appointed outlets. Do professionals really need Europe's intervention? So what next? Are we to see maximum speed limits imposed in F1 by Europe because speed can be dangerous? Surely the type of end user should be taken into consideration in these matters?