Finally decided to buy components and assemble a DIY headphone amplifier designed by Pete Millet http://www.pmillett.com/nuhybrid.html
It looks great and sounds great and it has enough power to pump 250 Ohm Beyerdynamics 990 Pro headphones.
I like the result, the only concern is that the quality of this concrete implementation is not good as it should be because I had to replace some passive elements with equivalents. So the next project is to measure frequency response manually using the EspoTek Labrador board.
