I can't comment on the Euopas, but I did move from an Anthem Amp 2 SE to Khartago Mono Extremes, and my speakers are Onix Reference 3, which are 4 ohm, 90 db, but go deeper than your Europas.
Overall, I liked the Anthem, but I felt that it never quite had the synergy with my Manley Shrimp pre-amp. Basically, even when I upgraded the Anthem with some highly regarded 6922s, the sound was just a little too "tubey" for me. So, either the Manley had to go, or the Anthem, and I really liked the Manley, which I bought it new, so selling it would result in more lost $$$, so I decided to give the Khartagos a try.
I've been extremely pleased with the Khartagos & their synergey with the Manley. Excellent clarity & sense of "space." The only problem I had was that the Khartagos didn't seem to have quite enough current for the Ref3s and didn't quite have the bottom end I knew the speakers were capable of. However, now that I have upgraded the speakers with the Skiing Ninja (Danny Ritchey designed) XOs, which bring the speakers up to 5 ohms, the bass is fine. And, given that your Europas don't go down to 28 Hz, I don't think this would be a problem for you.
Anyway, I know this doesn't explicitly help you with the question concerning the Europas, but in terms of the Anthem vs. the Odysseys vs. pure tube, it just depends on if you want a stronger tube influence or not. I know, I've been told that a truly good tube amp won't have a tubey sound, but in my experience the Anthem Amp 2 SE will not have the clarity of the Odyssey amps.
Hope this helps!
