I got to hear a lot of really great stuff. Thanks everyone for making it so enjoyable and to Gil for organizing. Some of my personal impressions:
HD-800: Exactly what I expected from reading. Incredibly detailed and analytic with incredible bass depth and wide sound stage. That, combined with them being one of the most comfortable cans that have ever graced my giant mellon made them highly desirable in my eyes. Only running off a Bottlehead Crack too. Very exciting.
Abyss: Wow. First of all, these are monsters. Huge and, ultimately, uncomfortable. Not a great first impression. While listening through a DAC-2, I understand why people covet these $5500 beasts. They're fast, aggressive, and very resolving. I would love a pair of the headphones with entirely a different band. I'm excited to see what the company does in the future, but at this price point and the lack of comfort, they are definitely not for me.
HE-6: What happened? They sounded boring and, ultimately, not much better than my HE-400s. Sad. I wanted so much more. The brief time I had with the HE-560 was MUCH more pleasant and what I expect. The 560s sounded like LCD-3 lite. I would love to compare them to LCD-2s in a more controlled listening environment. Both great cans. I'd avoid the HE-6, IMO.
Philips Fidelio X-1: Didn't see this coming. Great bass response, fast can, treble forward, and very clean. A little recessed in the mids, but overall, very impressive. Very comfortable as well. At $260, very impressive. I would recommend these to friends and lovers of classic rock any day.
Beyerdynamic T1: I wasn't expecting much here. They get a lot of love, but so do lots of FOTM and, in general, I don't really like the BD sound signature. I was wrong. Resolving, clean, and very airy. I really enjoyed these and consider them a strong competitor in their price bracket. I prefer my LCD-3s, but if I was looking at the LCD-2s, I might do a double take and have to look at these again. Very impressive.
Stax SR-202: Apparently, these can be got for $400 with amplifier. If that's actually even half true, these are a steal. Light, comfortable, BASSY, and incredibly fun. I was dumbfounded as I went in with relatively low expectations given the older look of the cans, they feel relatively cheaply made, and the lower cost. $400 for these is a steal. I'll be trolling the for-sale forums looking for these for a secondary home system.
UE-11 pro and UE-900s: Both sounded very similar in my listening time. Warm, soothing, and would never be fatiguing, which is what I expect out of IEMs. I want to be able to listen for 12 hours and never want to stop and these deliver. Even without a custom fit, the UE-11s fit my genetically deficiently formed ears well and provided more comfort and a WAY better seal than the 900s. I want customs. Damn you, UE. Damn you to the depths of my empty wallet.
Oh, and I still really want a FiiO X5. I didn't realize the wheel physically turned. It's so psychologically satisfying to scroll through lists.