I finally got my XM5 after some waiting and I can say that it was worth the wait. The build quality left a bit to be desired, especially for the price, but I guess thats the case with most portable amps. I am speaking about the internals, as I immediately opened it up to check out the opamps buffers. Also the way everything fit together was a bit simplistic.
The sound is however, the main reason I chose it and it did deliver, in spades. Bass was tight and clean, sound stage much wider than my old extigy. All the features are great and not gimmicky. I really do like the crossfeed, as it helps alot with some older music, that separate instruments completely between channels. It really does help, though the pot doesnt seem very sensitive.
I love how well it works with the dt 880s that I have, though at this point I'm not very sure whether the distortion that I am hearing at higher volumes is from the xm5, with the opa134 opamps or the beyers, the treble is definitely brite, siblance is under control but present. I'm getting the 8065s to see if it can control the distortions and hopefully tone down the siblance. Overall I am happy with the sound, and Im sure everything will even out with some more burn in. One thing I've noticed is that it definitely beats the headphone out on my onkyo receiver, amp wise at least. The headamps in receivers are most definitely after thoughts, sad really, so for anyone like me that thought receivers do movies justice through headphones, well, no.
Oh and one more note, I have sennheiser cx500s plugged in, though, I tend to think that the XM5 just outpaces it, coming from the recabled 880s that I have there is just so much that the XM5, beyer combination reveals in the source, I have high bitrate mp3s but exclusively test with flacs. Lol I guess the sennheisers arent very good. My wallet's running scared.