I've got an Apogee Mini DAC in my home system, and I sure like it. In my headphone rig in the office I also have a Headroom Balanced Desktop Amp with the DAC option, which together with my AKG 701 headphones sounds better than any other system I've listened to so far. However, I haven't compared the Apogee and the HeadRoom side-by-side in the same setup. But I am thinking about getting the HeadRoom Ultra Micro DAC as a replacement for the Apogee, simply because this DAC is the top-of-the-line DAC from the HeadRoom people and should therefore even sound better than the DAC in my HeadRoom headphone amp. Also, the HeadRoom amps/DACs come with sturdy power supplies, whereas the Apogee comes with a whimpy wall wart. And finally, while the Apogee relies on opamps of reasonable quality, the HeadRoom DAC makes use of the highly regarded 627 opamps.
Where did you get the "very highly" recommendation for the HeadRoom?