6SN7s would be inadequate to drive headphones by themselves, in my opinion. So that leaves a tube amp with a solid state buffer, which both the 24v Aikido and EHHA have. Broskies high voltage PSU is very good. Transformers sound better than capacitors to me, but I think it's mainly because of the lower output impedance. On the other hand cheap transformers sound like ass, and the price of good ones can be exorbitant. You may want to look at the L'espressivo as well.