I was surprised that there existed such differences between the models when I've tried them at meets against my LCD2 early rev1.
I wasn't a fan of the fazor versions, of either LCD2F or LCD3F. They just didn't feel as deep as my LCD2. But take that with a grain of salt. I'm sure they were fine headphones in their own right, Sometimes you just get used to the signature that you are familiar with.
That said, the LCD3 Classic I tried was better than my LCD2, even a bit deeper sounding. Even still, I didn't really feel any the lesser for having my LCD2. Also have heard the HD800 (love them) and the HE560 (these were great as well). The LCD2 still hits an emotional note (especially the lower registers!) in a way that none of those aforementioned headphones and my other headphones (HD700, D2000, HD250, 7520).
Still, my LCD2 doesn't always get the most listening, mostly out of practicality. Yet it always amazes me. Recently been testing it with a Chord Hugo 2 and my O2/ODAC - it is just incredible.
Also, I've owned the HD650 twice, and its an amazing headphone as well. It has its pluses over the LCD2 - one ultimately being comfort, which is a pretty big factor. it's one of the main reasons why my HD700s are listened to most.