after 5 months of owning the AD2000, i'm still enjoying them as much as the first day i heard them. the AD2000 presentation isn't for everyone, but the speed, dynamics, timbre and tone are excellent. like the K70x, the bass response may be a bit rolled off for some tastes. my other favorite HP is my modded Fostex T50RP. while the AD2000 sounds excellent with everything, i grab the Fostex when i want a little extra bass and am willing to sacrifice soundstaging. for electronica and acoustic recordings (classical and jazz), i reach for the AD2000.
every one of Asr's references and reviews on the AD2000 are spot on.
opamps are a personal preference. it's been awhile since i've listened to the OPA627, but i would say that it sounds closer to the B22 than does the AD8610. the AD8610 has a more present treble and assertive character than does the more relaxed sounding OPA627. depending on your partnering HP, you may prefer different opamps. personally, if i was driving brighter, more assertive sounding cans, i would stick with the OPA627 or AD843 - especially those that are peaky/ringing in the high mids and highs. i don't feel that my 2 preferred cans, the AD2000 and Fostex T50RP, have major issues in the high mids and highs. my personal preference is a more assertive and quicker sounding amplifier when driving these 2 HPs. in that respect, the AD8610 is "superior", but it's a personal preference. the AD8610 treble is present, but very clean without sounding harsh. also, you need to know the power supply voltage of your o11 before rolling opamps. the OPA627 can do 36V, but the AD8610 only 27V. 24-26V is the most common voltage builders configure a o11 for powering a M3, but i would double check with your builder.
Edited by fishski13 - 9/17/12 at 9:19pm