At the time they were the most accurate reference head phones for the price range. The price was dropping and then the whole Dr.Dre beats craze shot the price back up, not sure about now. Parametric equalizer?
I just thinking of a simple DAC with maybe a AKG K551 since it on sale locally for us.
Anyways, if you do somehow end up building either a Concoa 212 or a Matheson 3810 regulator, I'll be interested.