Happy to respond. I like ZeosPantera and was impressed by his enthusiastic review of the Aeons. I didn’t have the Quads at that time, so was comparing to the HD800S, Sivga P-II, AKG 361 and AKG K7XX. The HD800S are truly wonderful and for many tunes are a total blast. But because the soundstage is so wide, the intimacy of other tracks is lost, they are so open backed that any local noise gets through and to my old ears the accuracy means that they lack some warmth. I run the HD800S from a tube amp which does add back a little warmth. The Aeon reviews suggested that they had a moderate soundstage, more warmth and better sound isolation. I tried them as a potential adjunct to the HD800S not as a replacement. Shortly after I ordered the Aeons, APOS (a great company to deal with by the way) emailed me about the Quads. I’m a British ex pat who has been a fan of Quad since I was in my teens and who still has his Quad 303/33 amp/preamp/tuner rig, so I was keen to try them. As the saying goes “this changed everything”. Reviews of the Quads include ones that say “these are the best headphones I have ever heard” a sentiment that in a very limited way I would agree with. I would rephrase it to be “the best sounding to my ears and preferences for the widest range of the music that I like to listen to”. There are NO best headphones, they all play different tracks differently. The Quads have super bass and sub base which makes low strings, cello and bass have their rightful place in the orchestra, but for tracks that have heavy bass emphasis they are awful. Their transient response is terrific, and the sharp edge of a hard struck piano note and the snapping of fingers have definition that I don’t hear on my other headphones. On some tracks this makes it too edgy and uncomfortable. However, overall they do meet, for me at least, the definition of “best for the widest variety of tracks”. So many tracks have that wow factor when listening on the Quads. To be clear, my tastes are classical, vocals, jazz and some blues and 60s/70s pop. Not heavy metal or most avant-garde music. If I hadn’t had the Quads to compare, I would probably still have returned the Aeons as they were a little uncomfortable and just didn’t provide that something extra that would justify adding them to my collection. I am trying to get to the point where I spend more time listening to the music and less listening to the headphones, and I believe that the Quads will allow me to do that.
Hope that goes some way towards answering your question.
Best wishes and stay safe.