This is a great thread. I just found it. I didn't think many folks used old school stereo amps to drive modern headphones. Well I do too. I'm using an old school dual-mono Sanyo JCX 2900K Stereo Receiver made in 1978. The damn thing weighs about 65 pounds. I have an RME ADI 2 DAC plugged into the Aux in, and I use a pair of HD600s plugged into the headphone output jack. The Sanyo is 140 WPC so I cannot get pass 9 o'clock on the volume knob before it's too loud for me. But i have never heard my HD600s sound so good. The bass that others can't seem to find, well I found it. And the great thing about the Sanyo is it has a built in parametric eq, and separate bass, treble and mids knobs. I think I paid $450 for this receiver a few years ago, and it was sitting in the garage until recently. I have a few nice headphone amplifiers, but for my high Ohm headphones, nothing beats the Sanyo.