I know my thoughts will get lost in this huge thread, but I'll post a little bit about the Beyer T1 that I heard at the Colorado meet today. I tried them on Asr's Ayre QB-9 > Beta 22 and my PWD > ZDT amp.
It was a nice sounding headphone, but nothing spectacular. It seemed a little laid back and not hugely dynamic, but they didn't seem hard to drive. With both the HD800 and T1 connected to the ZDT amp at the same time the volume levels were similar and normal listening was with the volume knob at about 10 o'clock (similar to the LCD-2). In contrast, the HE-5 LE needed the volume knob at about 11 o'clock, and the HE-6 at about 2 o'clock for similar levels. The sound didn't change when listening with one phone and plugging the other in and out. The T1 seemed to wake up if the volume was cranked up a bit more, but I still preferred the other phones above to the T1.
Soundstage was not small, nor huge, but still smaller than the HD800 or LCD-2 and about the same as the HE-5 LE. Their frequency response seemed pretty level, without significant peaks and troughs. But they seemed to lack energy and excitement, being more polite sounding end of the scale. The HD800 were slightly more forward sounding, a bit more spacious, and a bit more engaging to me. Bass seemed similar between the two, and neither is lacking nor boosted. There might have been a tad more sparkle in the upper treble with the T1. With the Warren Audio double helix cable and ZDT amp, the HD800 are nicely balanced as well, and one person commented that my rig was the best he's heard the HD800 perform, and prior to today he didn't like them. So, some others who have compared the T1 and HD800 may not agree with my thoughts here, but in my case my re-cabled HD800 have good synergy with my Perfectwave DAC and ZDT amp. I do almost all my HD800 listening with that rig, even though I have many DACs and amps to choose from.
If I had to live with the T1 I could do it, but at times I might get bored listening to them. They don't do anything in particular wrong, but they just don't get me excited about the music. After a break from them (listened on my rig) I tried them again later on Asr's rig, and they still didn't do anything for me on an emotional level. It was kinda the same way with the Grado RS-2 or AD-2000 for me, where I just didn't get emotionally involved in the music was much as I would have liked. So, I've removed the T1 from my "would like to buy someday" list, even though they are not a bad headphone.