Good review! Pretty close to my experience. I would comment that the low output switch makes this little amp MUCH more useful; I get the same inky black background you did. And with my 650's, it is a very good match. I'm between 10 o' clock and 12 noon most of the time...more gain is not needed. This little guy is actually transparent enough to majorly benefit from anything you improve upstream of it; it'll let you know. IMHO, this amp sounds just like what it is...a pretty high quality little Class A/B SS amp.
Have to say I agree with Defiant00 as to burn in. Out of the box, my Magni had a pretty nasty treble peak...we're talking like 6db around 4-5Khz. This went away completely after being on a few hours, so I have to think something settled in, there!

Thanks! The low/high gain switch does make it much more versatile; I would be hugging 6 o'clock with my digital output on 5/100 if I had to use high gain with my low impedance headphones. 
Sound change with just a few hours of use?? That's quite interesting, I wish I had testing instruments to measure it straight out of the box vs. some burn in time. That would give something definitive at least on the frequency response side. I did feel that the Magni 2 removed some warmth and spiked the treble straight out of the box, but it went away after 1-2 days of listening. I just attributed that to the fact that I'm used to the warm and lush sound of my D5k, my ears/brain had burnt-in.