Hi ACST, I am new here and I just saw your question.
I just got both of them in front of me:
Teufel Concept B200 (USB-link to PC) and
Audioengine A2, which is connected to the PC via a Beresford Caiman external DAC (optical link to PC).
Surely, the Caiman is a higher quality DAC-solution than the Teufel built in one. There is also an additional [size=11.0pt]£100[/size] to be paid for the Caiman/A2 solution over the Concept B200 alone. Other advantages of the Beresford however are a preamp function, so you can adjust the sound level at the front (A2s have it at the back), it adds two coaxial inputs, an optical input over the B200 and importantly a nice Class A headphone amp producing a more spacious and detailed sound.
I was just briefly comparing both setups this way because normally you wouldn't buy a DAC and the Teufel speakers, given there is an Teufel amp but for the A2s, the external preamp/DAC adds functions making it in this sense a more similar system to the Teufel B200. The A2-speakers may need more burn in, so I may update this post later.
Update after 12 hours of operation and additional listening:
As a first impression, the B200 produces a clear, open sound with a tendency to be clinically clean. You feel a certain drive to increase the volume and to enjoy the dynamic sound. There is kick bass with pressure, sub-bass is present as well, noticeably more than with the A2. There is a nicely broad stage, but it is rather flat. Highs are a bit on the edgier side. Violins and other mids lack a silky shine. What I miss is a certain warmth and breathing of voices, for example when Katie Melua sings Mary Pickford. Voices and instruments populating the mids are present but they have little body. Over all, the sound is great if you like a chill type of sound with dynamics.
The A2 has a warmer sound and voices have more body. The sound is more natural as well. The stage is wider and much deeper with more details, for example in Michael Jackson's Thriller. This is probably emphasized by the Beresford Caiman support. In comparison to the B200, Bruce Springsteen is not cold anymore and moves closer to you on the stage. This is the big advantage over the B200. On the other hand, the bass has a little less punch and the deep bass is mostly missing. The lack of deep bass shall be forgiven given their tiny size. Highs are not sharp, rather comfortably silky, which makes violins enjoyable. The basic representation is like this, also without this external DAC. The sound is neutral and natural. Norah Jones and Vivaldi say thank you.
In summary, both do very good jobs in their rights. The Teufel B200 produces a cleaner, more dynamic but also harder sound with a wide but flat sound stage. The A2s sound more natural and warmer with an even wider soundstage. Although I like the Teufel temptation, the A2 is my favourite due to the the natural sound and the ability to shape out voices.
I hope you enjoyed my speaker impressions =)