Here's my impressions, I'll update them as time goes by and as I get my thoughts together:
iBasso Viper - w/ the correct op-amps, sounded very close to the Predator, the only difference was that the Predator had a little different decay, sounded more realistic and pleasing but one doesn't have the Viper and the Predator side by side to compare, you'd never notice. Overall impressive portable, I wouldn't hesitate to get one if I was in the market for a portable.
Earmax Pro - the tiniest tube amp I've ever seen! Really smooth sound but still accurate enough. Worked really great for cans that weren't too current-demanding such as the HFI-780. On the other hand, cans like the D5000 and the HP-1 caused some clipping/distortion when cranked, per HiFlight this was due to the said cans demanding too much current. For some reason, my HP-1 had little to no synergy w/ this amp.
Nick's Adcom CD Player - great sounding CD player. Very smooth and sound seemed to have more authority compared to my iMod (duh!).
Benchmark DAC1 Pre - I used the headphone amp on this unit w/ my ALO-780 and the Denons. Surprisingly, it was very decent as a headamp but sounded like a solid-state amp as expected. Build quality was very very good.
Denon D5000 Stock - a little too much bass for me and I thought I was a basshead!
Denon D5000 Markl Modded and Jena re-wired - this is the second time I have encountered this can at a meet and for some weird reason I seem to sub-conciously snob this can and not give it ample time. Maybe deep inside me, I know it might wow me so much that I would have to buy one

Anyway, with the little time I spent on them, I noticed much better bass control vs. stock and a little wider soundstage. Overall nice cans, I wish I spent more time w/ them.
Denon D2000 - another can I spent little time with. Only comment I can make is it's very well balanced and didn't have the excess bass of the D5000.
Ultrasone 2500 - the first can I've picked up and couldn't stand for more than a minute and I'm really not the criticizing type, I try to look for the good in everything. High frequencies sounded way different from what all the other cans produced, as if the recording was a different one.
mrarroyo's MPX3 and Monarchy DAC - awesome rig! Smooth sound without sounding too laid back. The tube output of his DAC really killed the SS output, seemed as if the SS lacked something the tube section brought to the table.
Sennheiser HD650 w/ RAL recable - sounded a little too dark at first esp. when you switch from the D5000 to this but I gave it more time and I found a certain chemistry/fondness for it. Non-abrasive highs and deep bass really floated my boat. I liked the non-fatiguing nature of this can.
Grado HP-1 - I just got this in earlier this week, together w/ my Melos SHA-1. The most detailed can I've owned, beating the K701 I just sold off. Came w/ bowls and this seemed to cause the bass to be a little lacking and I found this can to be fatiguing at times (it has tipped up upper mids/"lower" treble range), especially when I try to "rock out" w/ them. As time went by though, the Melos probably settled down and it's getting a lot better. Awesome w/ Eric Clapton, Bob Marley and other tunes that had background singers. On one song that the title escapes me at the moment, I could distinctly tell that there were 2 different women backup singers, one to the left, one to the right and one was definitely farther from me than the other one. It was really cool to experience this. Hopefully flat pads make this can shine better and tame the higher frequencies.
I had a blast during this meet, it was really cool to meet some fellow FL head-fiers. There was a very good variety of gear to try out but I gotta admit, HiFlight's exotic Sony headphones and his various amps impressed me a lot. Everyone was really nice, especially to a noob like me w/ all my stupid inquiries

Thanks again Nick for putting this meet together, hopefully we can do it again sometime soon!