Yeah, the Micro Amp is really great.
Three and a half years now, I've had the Micro Amp (the 2005 version, which is not even as nice as the one you can buy today). And nearly that whole time, I've intended to upgrade to HeadRoom's higher-end stuff, on the basis that if they can do this at the low end, just imagine what they can do at the high end. But I keep getting stymied but not being able to really find any flaw in what I have or to imagine how it could be better.
(If you read that linked post, don't worry: I've since moved the headphone system to the bedroom with a Squeezebox Duet, so I'm not being perpetually cut short of sleep...)