I just got the Polaris (to power HE-500's I also just picked up), and I'm just super-happy with this decision. I don't have a rich assortment of amps to compare against (just my Schiit Magni and a friend's O2). The amount of detail retrieval that just moving from the Shiit to this amp - I couldn't believe the change. I fully expected that with these headphones (which were completely new to me), that I would need to spend time A/B'ing the 2 amps to hear what, if anything, the Polaris would bring to bear.
Boy was I wrong. I was immediate awe-struck. Female voices just sounded "right": they had a better tonal balance; they now had air around them which really gave them life; I could actually make out lyrics that I never understood before (I *really* didn't believe that when I first experienced it - I had to relisten to some tracks again to realize that I was actually finally hearing what she was saying).
Instrument separation was much stronger. For the first time since my 20s (when I was hanging out in high-end audio shops), I actually stopped "actively listening": meaning I sat back, closed my eyes, and could just *hear* the entire musical presentation. All my experiences before this with headphones required me to focus on listening to different parts in the music - be it the layers of additional vocal tracks, or tracking all of what the drummer (Tool's drummer can be hard to follow on other setups), or all the small additional instruments added for color and texture. For the next few hours, I just re-listened to those tracks which had been played endlessly and didn't have to 'work': all that detail was made so completely evident.
I'll stop now as I don't want this to come across too strongly. I can only assume there are amps which can take detail, sound stage, separation, etc. even further. But for the price paid, holy cow. What an amazing amp.
I only have ~12 hours on it. I'll need to spend a lot more, get "acclimated" to it, then go back and try the Magni and O2 again, just to see what differences I hear there.
BTW, Jeremy was awesome. Exactly what I would want for a salesman of any product. He knows his stuff, answered all my questions, obviously thought highly of his product but wasn't pushy and never seemed to be over-selling. He had some great recommendations for tubes for my DAC. He actually swayed me away from the Ember since the DAC already has a tube, and trying to match & align the DAC tube with the Ember tubes could be "difficult".
* full disclaimer: I'm going from JRiver -> USB/SPDIF converter -> Cal Audio Sigma II DAC (yes, that old one) -> Polaris -> HE-500s. The Cal Audio DAC has a tube output stage.
