I am a bit rusty, but the HD6’s are not high-impedance (which typically is in the 300-600 Ohm range), but indeed a bit higher than some typical DJ cans. My HD 25-1 IIs are 70 Ohm or so. And those go plenty loud (can’t push them past the halfway mark usually). My controller (MCX8000) has a 150mW power output. So that would be 2.8Vrms if I am correct.
The HD6 has a 112dB/1Vrms sensitivity, so I’d say more than 120dB at full power. I would think plenty loud enough (if it isn’t you have another problem, namely not destroying your ears!).
Should you still decide you need amplification, there are plenty of portable solutions, think some in-line ones even (which are generally unpractical as they make your headphone connection stick out even further.
Pretty much for high-volume DJ use the quality is really not an issue. I’d even look for something used. Should only be a couple of bucks.
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