bigshot
Headphoneus Supremus
I hate to tell ya, but a specific answer to this area can't be given because its all relative to what your sources are and just how analytical they are (amps/DAC's).
You quoted a specific cable and amp (Moon audio's V2 black dragon and ALO) and a specific set of headphones (HD-800). Let's start there. What does the cable do? Better response, distortion, dynamic range, what?