@Fourteen: About which Violectric model I may help a little because I was able to test some models on CanJam Europe in 2015: HPA V200, HPA V280 and HPA V281. Headphone has been the Sennheiser HD800, and I was able to use my own music tracks for testing (*.flac files).
The V280 has been superior to V200 basically because it has XLR-output, which gives better sound than the unbalanced one. This was surprising to me because right at the V280's output a short (few centimeters) XLR-to-stereojack adapter was connected.
Then, unfortunately, I tried the V281. Knowing its price it was my (little) hope not to hear a difference significant enough to seriously think about the associated additional invest. But, well, the V281 was adding quite a lot and my very first thought was "shit, I should not be have tested". However, in discussion with Violectric's CEO Fried Reim he mentioned that not everybody testing both V281 and V280 made the experience to hear any difference... And, I'm not going to describe the amp's sound as this is quite difficult, just, Violectric headphone amps are from my point of view very neutral and have full control over full frequency range.
So, choice is up to you - in particular with respect to budget limits. For same reason I personnally put descision off: V281 and HD800 (which has been my conclusion after CanJam visit) sum up to around 3300€, which levels priorities ...