So I just grabbed a pair of these from Amazon this past week since they were on sale (maybe still are?). Only have about 15 hours on them so far, listening a few different sources (Sony NWZ-A17, Chord Mojo, Audioquest Dragonfly Red). I think so far my favorite source with these is the Dragonfly Red. It adds a bit of warmth into the mids that I feel are a bit lacking with the quad drivers.
I also decided to swap out the silicone tips with the 13 mm foam tips, and was surprised to find that they significantly changed the sound signature, although I'm not sure if it's for the better or worse. The foam tips seem to tame the treble down a bit, and make the bass more prominent. I do feel as though a good bit of detail was lost after switching to the foam tips, but of course the increase in sound isolation is great, since the silicone tips don't offer much.
I have a Fiio X5iii on the way that should be delivered next week. Will be interesting to hear how they sound with that. Compared to my beloved Senn IE80s, it's very hard for me right now to say which I prefer. The IE80s are definitely a bit richer in the mids, which I always tend to gravitate towards. It's nice having a change of pace with the quad drivers, however. By comparison, it now seems like the IE80s sometimes have a bit too much bass which can bleed up into the midrange at times.
Has anyone tried the quad driver with the Comply foam tips?