concise: take Elantec EL2001s and stick em in the feedback loop of an Analog AD823, powered via two 9Vs in series, thru a TI TLE2426 rail splitter, with nice system/local bypasses and a Noble AP series pot. Extremely battery friendly for high-ohm cans, and enough swing for a few hundred milliwatts.
Result: Deep & Bright. Much 'hotter' than OPA134/BUF634 pair. Treble will get very agressive on bright headphones or crappy recordings. Actually it's an agressive amp all around. 'Smooth' is not a word you'd use to describe the sound.
As quoted by a friend here who auditioned it for a couple weeks... (paraphrased) "Makes HD600s sound like Grados... too agressive for me. Makes MDR-7506s sing though."