Listening fatigue most commonly caused by distortion/compression, which occurred most frequently at (you guess it) the end of chain, your speakers, being the largest mechanical device that produce the actual sound. And the most common cause for distortion/compression in speakers is underpower (they do not get blown by tons of clean power)
This is the interview with the 4367 chief designer (as well as their 80k everest) Grep Timbers https://positive-feedback.com/interviews/greg-timbers-jbl/
He uses 4x Parasound JC1 (800w into 4ohm each) 1 for each woofer in his everest (tube for high). So lets say 4367 has 1 15" woofer, at least give it 400w high current power.