Joel, Bart, the 300 ohms of the Senns is a tough load for the Dragonfly. While the Dragonfly can drive them, I also have one, it does not truly do them justice.
My favorite combo for the HD6xx is either Class A solid state pairing or tubes. Tube amps that can drive the HD6xx well are especially a synergistic combo.
Joel, looking forward to your impressions with the Meze 99!
