It's a steel chassis, not aluminium.

Great review! I used to own the combo with the HD600s and pretty much agree with everything you said, minus the treble (always thought M&M were slightly bright).

Thanks man. I could be wrong with my impressions. So far I only tested with one proper headphone. I have a couple of stock apple ones, and a gaming headphone. Not musical enough to make the amp justice.
I will have my friends grado sr80i and some other Ultimate Ears next week.
I may change one or 2 things...