That's certainly an option, Swan.. I'd opt to use the TD-11's "tube out" to a nice, transparent solid state amp (that provided ample current into low impedance loads.. which is what most planars tend to like). Perhaps something like the Schiit Magni or Asgard 2. A few people have run a tube buffer to their Emotiva XDA-1 (with the HE-500 running of the XDA's speaker taps) and found the combo to be excellent. But really, I'd be more than happy with the TD-11's headphone out.. I did have the HE-500 and TD-11 at the same time (for a very short period) and remember the HE-500 to sound superb from the TD-11's headphone output.