Interesting. I have the Noble 4C, though I haven't tried it with the Onkyo or Teac. At least for the UERM, I don't think neither the Onkyo nor Teac has a muffled sound signature. The impedance curve of the Noble 4/4C is known, and it's actually less susceptible to FR changes due to output impedance of the source amplifier. Yes, however, both the Onkyo and the Teac are definitely warmer devices than the ADL X1 (was I the one that "panned" the X1? Because I don't like it, and I might've mentioned something about the Onkyo and Teac being better units). I can understand if you come from an ADL sound signature, or something similar like the ODAC, that the sound might be too "relaxed" sounding, but I feel the Teac definitely has adequate detail levels, to go with a warmer signature and a smoother treble response. Again, I only listened to the Onkyo long enough to think that it sounded somewhat similar to the Teac, because I knew I couldn't do a real comparison between the two, so I wouldn't be able to remark whether the two have distinct differences. I don't recall exactly, but one of the Japanese bloggers might've mentioned that the Onkyo sounds warmer than the Teac somewhere. Personally, I couldn't really make a declaration either way.