Got them not long ago.
Yes, they are really need good amp - Xonar Essense can drive them more or less only on last level of amping. They have lack of bass cause open construction, but have very light and clear mids and highs, good soundstage. Building quality is good, they are comfortable. Really interesting headphones.
JeckyllAndHyde, thanks for photo of drivers. 70mm - they are really big and beautiful.