I disagree with so much of what you say that it's pointless to start a debate with you because it will never go anywhere positive. My intent was to help someone make a decision, because he asked for help. I didn't push advice on anyone. Your motivation is to discredit anyone who doesn't agree with you. My motivation was to help someone who asked for it. Your motivation is to discredit me because I disagree with you.
These are facts:
LD is spec'ed at 100 mW into 32 Ohms
HD-400 sensitivity is spec'ed at 93 dB at 1 mW, with rated Z = 35 Ohms
For sake of this approximate calculation the Z difference is within 10%
It doesn't make any difference what the voltage is at the input (within reason) because the volume pot is before any amplification. 100 mW out will drive the HD-400 to 103 dB SPL before clipping which I define as 10% THD. To me that's ear splitting volume but I do understand that others may need or want more.
I never stated that I tested the HD-400 with the LD MK3 so of course I can't be 100% sure if it will get loud enough for the end user. This was implicit in my comment. All I can say which I did is that it should be more than loud enough (103 dB SPL). Again, this is my educated OPINION based on my ears, my own experience with phones I listed and the specs of the LD and HD400. I think most readers of the posts (except it seems you), would understand.
I just want to make sure readers of this thread (which I hope ends here) are not mislead by your negative and (in my OPINION) misled comments.