Indeed. The HE-6's treble presentation can be problematic with solid state amps. I consider it to be a mostly neutral treble, but as with other headphones with neutral treble, they can sound shrill with many solid state amps. If I were buying an HE-6 myself, I'd shoot for a Ray Samuels Dark Star or fully upgraded Woo Audio WA5 with aftermarket tubes (the ones Woo offers should be a great place to start) even though I've never personally heard either. Or, if I couldn't afford to drop $3k - 10k on an amp, I'd look for a good tube power amp.