OK, so after that great Bears win yesterday, and with almost a full 24 hours break-in on the Opera, I decided to do some camparison of the Opera to the HA-2 MkII/SE, which has been my long term reference and main amp, and which no other amp has ever come close to for me in terms of performance. And what did I find? Well...
The Opera is a tremendously good amp. But it does have a somehat different sonic signature than the HA-2 II/SE. The Opera, while still very detailed and transparent, is warmer sounding than the HA-2 II/SE, and to enough of a degree that it became impossible to say which amp was better without choosing a companion headphone. With the Darth Beyers, I preferred the HA-2 II/SE. With the 05/06 DT990 and DT880, I preferred the Opera, where the additional warmth was welcome. The Opera seems also to have a little less treble energy than the HA-2 II/SE, which again made the above headphone pairings more attractive. I also preferred the Opera with the JVC DX1000's. But from my memory of the HD650's, I strongly believe they would fare better with the HA-2 II/SE.
So there you go. Since it has a USB DAC, my intended home for the Opera has always been as an upgrade to the Aria in my office, where I listen with DT990's, and so it is picture-perfect in that application. But my "main" rig, which is V3 Darth Beyers, the HA-2 II/SE will remain.
I'm sure the Opera will continue to improve, also, and I will report back if it does. It's a phenomenal amp - listening to it right now with the DT990's and I have to confess I get distracted the music is so good...maybe this is not such a great work amp after all