I traded my rega ear to norm for a classic (which is running off an elpac and using AD8620 op amp), and have been nothing but impressed with the sound thus far.
I own a behringer UB802 mini-mixing board, which has an integrated headphone amplifier, and it was (IMO) on the same level as the rega. I could hear a little more distortion on the 802, as well as some clipping at moderate volumes, but they both had equivalent punch and clarity.
I got the classic hooked into my sistem, and started listening. I started noticing details that were not there before, noticed that I was hearing bass on songs that previously lacked it, and now my DT-770's are VERY bassy on songs that call for it. Previously I hadn't seen what the big issue with them was, they seemed relatively balanced out of the rega.
The classic behaves nicely with my grados, and gives me a ton of details, has good punch, and makes my headphones sound like they're breathing. Finally I'm getting a good headstage, good texture to the music.
I'll leave a disclaimer at the end however, this is only my second mid-fi amp that I've lived with for an extended period, but I'll be taking delivery of a nice pimeta in the not too distant future, and will post more impressions later, comparing the two.
What I can say for certain however is that my classis vastly outperforms my former rega with all three of my headphones (SR-125, Sony CD-1700, and DT-770/250).