I used the HE-4 for a few weeks while preproman had them in for a HiFiMan shootoff. The 5LE, 6, 4, 500. The hp jack on the Hilo is decent for an accessory of a good DAC. I also used my Singlepower Extreme with not so good results. I could run the 4s with the volume all the way without distortion. But they sound better on a speaker amp. The bass is hard and fast and the soundstage is better on them as well.