Received them about a week ago. I will be shipping them tomorrow to Poetik. I've spent a bit of time with them.
I've been using a mixture of sansa clip+, clip+ with PA2v2, and computers. As far as amped vs. unamped, I believe they do sound better with it, but I honestly can't say if that "last 5%" is just in my head or not with these phones.
I gotta say I feel like this product almost lacks an identity. It seems the only way you can easily tell them apart from the re-262's is by the "272" labeled on them. The box it comes in, the accessories, and the design of the IEMs are all identical to the re-262. And honestly the sound, to me anyways, doesn't sound very different from the 262 either. The difference is there, but it seems for their new "flagship" they might have changed a few things up and given it it's own identity. It seems most people feel these are a slightly better re-262, but a whole lot more expensive (in comparison anyway,) and I agree.
It seems like a lot of the reviews have been mostly middle of the road with a mix of negative. The only real higher-end IEMs I have to compare them to are the re-zero, re0, and re-262. Keep that in mind when I say these are fantastic headphones. They are all about the details, and I'm a nut for details. I am as interested in everything happening in the background as I am the foreground. Vocals are beautiful on them, as well as most instruments. They're a lot more focused on the highs than the mids like the re-262. The only real downfall for them is the same downfall for all hifiman IEMs, the bass. It's not bad, it's never been BAD, It's just not as good as the mids and highs, and you really only notice it on songs that are defined by the bass. Let me put it this way, you can HEAR the bass and it's accurate and whatnot, but I don't FEEL it.
I can definitely understand people who think they are TOO "clean" or analytical. I think these were made for laying down in the dark and listening to them, if you're not giving them 100% of your attention you kind of forget they're on your head, and it turns from music to just noise. However if you are focused on the music they are pretty much awesome.
If these were $150 right next to the re-262's, I'd probably pick these, but they aren't. They're $100 more and I'm not sure exactly why. Same case, same design, same accessories, slightly better sound (to me anyways.) I think $175 would be a great price for them. If I simply bought these I think I'd feel a little bit cheated at $250. Bottom line, fantastic IEMs, but not worth the $$ over re-262.
Well, 272 has a low impedance. If it can perform unamped the same as 262 amped, then it is a winner.