Weird, my serial is 311XX. Also, are the piercing highs normal with non-ideal amps? I know warm / high-impedance (output) amps can help, but I'm talking about 5-7 dB here. After EQ they still sound bright (the Amirons / LCD2s sound muffled in comparison), so it's not me wanting to turn these into dark cans. At the moment I'm using the iFi micro iDSD BL. Would buying the A20 make a difference? There's no proper way to buy a Bottlehead Crack here in Europe and HP8 / Elise is too expensive.
I have 14 days to return, but I'm in love with everything other than the highs, so it'd be great if that was solvable with a matching amp.
You could try the Feliks Audio Echo or Espressivo MKII