On a positive note, if you have one of these and are wondering how it drives 18ohm Deva/HE5XX HFM planars, it does great IMO.
I have mine in low gain, driven by an LG V20 'tricked' into 'high impedance' 2V into LS. LS controlling volume. No apparent clipping or distortion up to ear shattering levels. Volume knob still has a ways to go at the 'shattering' point (more than with HE400i) - plenty of headroom even in low gain. Well matched for these HFM IMO.
Do watch your listening volume. Without distortion to make you reach for the volume knob, it is very easy to be listening at potentially damaging levels and be unaware of it.