Almost nobody has heard the he560 or pm1, lcd-x is still pretty fresh and not many have heard, has a bit of hype train going on but it's probably still a good choice for most people. Th900 are easy to drive but have too much bass for me. Hd800 are not so much hard to drive as they are revealing of bad equipment (yes they need an amp); audeze are more forgiving.
shchCompletely agree, took awhile for me find an amp to really bring out the HD800, the Questyle CMA800 that Massdrop recently featured is one such amp. Also like them on the Bryston BHA-1. Tried them with a Schiit Lyr and a Burson Audio Soloist, Soloist almost hit it but not as well as the other two amps. So yes, agreed, the HD800 is very much amp dependent to sound great.