Holy Moly guys!
I Just got my HRT microStreamer today, and am listening to lossless ALAC on my macbook through it with my ER-4S. This is the absolute best the ER-4s have sounded since i got them. Absolute night and day difference with the ER-4, both due to the amp on this little thing and the lossless, much more depth and no artifacts in the sound... more bass too, oddly.
Just goes to show, you gotta feed the ER-4s high quality music to really get the best out of them - no compromises.