Well, that's all fine and nice...but the thread is asking for impressions about the HeadRoom Micro Amp. Perhaps you could chime in with some info re) how it compares??
I've heard the Micro on a couple of occasions now. It's available with either the Micro (which I've heard at meets) and Desktop (which I'm upgrading my Coda to) modules. I've also, of course, spent significant time with the Coda (its predecessor).
I'd say that it's a pretty nice amp. I think that you'll find it pretty comparable to the RS SR-71. It's hard to say how it compares to a Pimeta, PPA, or other DIY amps, as so many variants of said amps are available.