The higher impedance Audezes are good on the 3F (note that Audezes' impedance will be different depending upon revision). Especially the latest high-impedance Audeze formulations which have higher Z than prior generations (LCD-2,3). The 3F has Z out of 5-ohms Into a 20-ohm LCD-X, that means 5 / 25 (20+5) the voltage is wasted as heat. Not only that, the 3F isn't that powerful. So double whammy. Not much power, and good portion of that power being wasted as heat. The idea behind 3F was a minimal design for the most transparent delivery of the signal to Focal headphones. The LCD-X will sound soft, lazy, and laid-back from 3F compared to even a Magni 3+. The Liquid Gold X is a monster into lower-impedance loads. At 33-ohms, about 6W of power which is a fuckton (into 33-ohms). I bet even if the gains are not linear into half that impedance, it's still a ton of power. I suspect the Liquid Gold works great with Audezes because of the combination of power/current and it's voicing. No necessarily. However, the newer low Z stuff (LCD-X, LCD-5) may be more challenging in this regards, and will require high current amps capable of powering almost speaker-like loads.