Haven't heard the Portaphile, but I have heard the HE-6 and I doubt that deafening levels can be achieved with this amp. Perhaps your ears are more sensitive than mine. I'll bet that at full power the batteries will go kaput very quickly. Sharing one channel for a virtual ground is IMO a serious flaw. It will lead to clipping and increased distortion on certain volume peaks/transients when under more difficult driving conditions.
My Asgard 2 can drive my HE-500's to 1 Watt which requires almost 6.2 Amps which is far more than the 250 mA that the Portaphile can truly deliver (due to the common ground channel). The HE-6 will require 7 Amps at 1 Watt. Supplying 250 mA can be loud with the Portaphile/HE-6's but with no headroom so I would expect distortion when listening loud, especially TIM and grungy bass on peaks.
How did you get 6.2 amps? Watts = I^2 x R, so 1 watt = (.162)^2 x 38 ohms (HE-500 resistance). So,wouldn't that that be 162ma's and not 6.2 amps? It would be 6.2Vs though, maybe that's what you meant?
Edited by Pappucho - 1/26/14 at 10:10am