LD Systems HPA 4

It´s fairly cheap. It´s compact and it takes four headphones.
I wasn´t expecting so much when I bought this considering the price, but the HPA 4 has turned out to be a headphone amplifier well worth the money. I´ve been powering my AKG K701s and some other gigantic headphones with it and it has worked very well.
I would definitely buy again if it ever broke, but it´s been soldiering on for a couple of years now. I wouldn´t say it´s built like a tank - like the Superlux HA3D that I also own, it does however rival it in sound quality in my opinion - at least with the headphones I´ve been using.
I recommend this product.