Not sure what the difference between the Asgard 1 and Asgard 2 is, but I thoroughly enjoy the Asgard 2 with my planars.
With the HE-400 and on low gain the soundscape is somewhat wider, more space, on high gain the midst come more forward and it's a more in your face sound.
I'm sure other amps/dacs give their own signature to the sound, but for me this works and is end-game for me.
(though I'm not ruling out getting another dac like the Bifrost, if only it would fit below the Asgard 2).
I'll second the low-gain versus high-gain. The lower is my preference.
I wish I understood more with regards to headphone amplifier topology (I am here, so perhaps there is hope), but to my ears the 12dB of feedback in low gain mode is doing the sound some good. And there is still plenty of power available to drive my most power-hungry planar.