Received my quads this morning.. perfect fit right out of the box.. I'll post some more impressions later but I'm COMPLETELY BLOWN AWAY by them. Thanks again to ericp10 & everyone else who provided the detailed reviews and thoughts.. to my ears, they are everything you all stated and more.
I don't understand where all the talk of the treble being insufficient or too smooth is coming from (oh wait, I do.. different ears, yadda yadda). Being a fanboy of the RE0/DBA/GR07 (a listener who loves crisp, extended, highly detailed treble), the quad's treble sound more realistic and accurate than any of those phones. The treble doesn't sound artificially boosted or have some kind of added sparkle to give the illusion of clarity. The treble is on the smoother but I certainly don't feel like I'm losing any of the clarity or microdetails vs brighter, treble heavy phones.
I have never heard such smooth (yet highly detailed), clean, balanced phones with jaw dropping clarity in my life. It handily craps on every universal I own. I can't get over how clean, controlled, and effortless everything sounds.. the bass is simply legendary.. soooo deep, impactful, and well textured.. but never dominating any of the other frequencies.. it's simply stunning. It will only get authoritative when called upon so all music doesn't have a bassy tinge to it.
I don't hear any kind of heavy timbre slant to the quads.. they sound very balanced to me.. not warm, not cold, not thick, or thin.. perhaps every so slightly forward but it not close to fatiguing in the least.. For GR07 owners, I can comfortably conclude these are the logical upgrade if you want a custom.. and they spank the GR07 with freakish ease.
It's going to be quite tough going back to listening to universals after getting these. I definitely understand why customs are so praised from a comfort standpoint.. there is no equivalent. They simply disappear when you have the right fit. I didn't get any special tips for the Quad.. everything is stock.. from the wire up.. I also love the fact you can listen to music at a lower volume with customs since the seal is so much better.. something your ears will thank you for as you get older.
Take any & all statements from me with a grain of salt cause these are my first customs.. and most likely only ones considering how perfectly suited they feel to my taste. If I ever do get another set of customs, it won't be for a very long time and it'll be when I'm ready to drop over $1K (just don't tell my wife).