Owned the EPOS ESL3's for a while and they were not bright sounding at all ... perhaps a little boxy sounding, which was more due to how I had them placed. I had them paired with a vintage Marantz receiver and Signal Speaker Cables & Interconnects. In the HIFI review of the EPOS, their only caveat was to pair them with quality amplification, in fact better amplification than you would normally provide for $300 speakers. Can not imagine why this combination would sound so bright that your ears would hurt. Are the speakers connected in phase? If you are willing to do some research, there was a thread either here or in Audio Asylum in the last month, about an ESL3 owner who took apart his speakers and removed some loose tape or something similar to that.
Regards, Rich
Regards, Rich