>>106326141
Open backs? Try out Senn HD560S (basically HD660S driver in HD5xx chassis) - they measure super flat (other open backs typically have bass sloping downwards from 100hz). They are 160ohm BUT like 104dB/mW so they should work fine on E10K.
You might want to EQ them since FT1s are V shaped - boosted at bass, boosted at high treble.