This is a pretty decent amp. I don't have a monoblock config. I use this with my HD6xx and K7xx and sometimes even with my HE560. It just barely powers the 560 though. The best part is, I don't sense any distortion anywhere even at full volume. The amp becomes reasonably hot to touch after a around an hour of use.
It has a pretty decent sound quality. Has a very relaxing sound signature. Slightly rolled off bass & treble. Sound stage is pretty wide and lacks depth. Still somehow manages to do a decent job layering sound.
This is not a power monster, beware. What it does give, it gives without distortion (that I could detect).