I'm quite shocked that someone such as yourself who clearly has some very nice kit has got sucked in by the power = volume camp. Power required to achieve volume is an almost worthless calculation. HIFIMAN recommend a MINIMUM OF 1 Watt for the HE500 and that is straight from Fang himself. Running the HE500 on 343mV ( probably closer to 450-550 with an impedance of 38ish) is criminal, its like having a Porsche with a Lada engine in it.
Most specifications are next to meaningless to as the designers can use clever mechanisms to lower a certain published specification while butchering non-public specs. My example being using large amounts of negative feedback to reduce THD but degrade the sound quality, which was the rage in the 1980’s.
Fair point about the two box solution being more flexible upgrade wise, completely fair point.
Either way, it honestly makes very little difference to me as im very happy with my set-up. I would just hate to see someone who has read so much good about the HE500 to end up being disappointed.
Without going too much further off topic, it's well known that HifiMan is consistently off on their specs, so please refrain from telling me i'm "getting sucked in". Second, that table i posted is based on actual measurements, not specs. I do agree that amp/DAC specs do lack how they came upon their conclusion, it's too bad manufacturers don't provide more detail.
You're also right that it does make little difference as long as you're happy, I never bashed the Compass 2 but i did state objectively as i could about components used and specs that were missing. I doubt he would be disappointed with either setup.