To add to my earlier comments, I've been listening tonight to the O2 again using the more resolving DIY silver interconnect for the first time. As expected, it didn't really change my conclusion with highly dynamic material like the drum solo on "Yesterdays" - on which the O2 (with my DIY all-tube amp using 6SN7 output tubes) still can't resolve, for example, the sharp attack of the snare thwacks anywhere near as well as the Audeze, and makes the piano (which is being played loud during the drum solo) sound somehow too generalized and over-reverberant compared to the Audeze, as if the mics were positioned too far from the strings to catch as much of their play of overtones. If this is an artifact of inadequate power then I will re-evaluate when a more powerful amp comes my way. However, on listening to the following track, a guitar- rather than piano-accompanied ballad called "Just for a Thrill", the relative merits of the two phones show themselves more evenly divided, and here I personally prefer the O2 (at least sometimes!). The Audeze, while seemingly more clearly representing the track's spatial detail (differentiating the slightly greater or longer reverb on the voice from that on the instruments for example), is a bit more clinical-sounding through the solid-state amp, and even through the tube amp it doesn't have quite the liquidity and delicacy and also the "size" of the O2's representation of sound in space. By size I mean a sense of the pervasive space or volume of a room that somehow situates the listener in relation to the performance itself in a very beguiling and intimate way. Exactly how much of all this is due to the different amps and how much to the inherent sound of the Audeze and the O2 I can't really say, nor can I say which is truest to the recording. If I could hazard a guess, based on how I imagine it was mic'd and mixed, it would be that neither phone is exactly right, that the "truth" lies somewhere in between. So once again it comes down to personal taste. If the O2 is indeed adding its signature to everything, that would sometimes work in the music's favor for many listeners, but not always. If the Audeze has a signature I think it is more subtractive - the Audeze might not be capturing the last wisp or two of airiness, but then again that might be largely an electrostatic coloration. (I hear even more of something like the same thing on my Lambda Signature, but it does this by exaggerating the presence range, which the O2 does not; OTOH the Lambda does better at resolving detail on the "Yesterdays" drum solo, probably because it has less bass along with more highs.)
For me the Audeze are excellent close-up phones - if you like sitting in the first row and reveling in dynamics, power and detail (as I do most of the time) they can dazzle like sunlight glinting on rippling water. And I (tentatively) think they more accurately represent a greater range of music and qualities in music. The O2 have their own kind of subtle detail, and can create a laid-back sort of moonlit ambiance that subjectively seems absolutely right, even magical. At this point I wouldn't want to be without either of them.
Edited by tonereef - 7/13/10 at 1:32am
Now with the Mk2 there has crept up an issue as Stax has altered the design from the very first units and plugged the ports making the bass more like the Mk1 SR-007. I had a few of the very first A/Mk2 units and they had the ports open which made them sound rather poor to my ears. This resulted in me inventing a mod to make them sound more like the Mk1. Fast forward to CanJam where I heard two Mk2's which both had the ports closed and the bass was back to normal. What they did I don't know (I didn't want to rip the earpads off at the show) nor when the change took place. 
The T2 is a nice amp but it simply doesn't have the power of the BH or T2DIY due to the chassis design (as in Stax couldn't run the EL34's at full power) and the PSU is also a bad joke in comparison to what's used on the DIY T2. That doesn't mean it isn't more powerful then almost every other amp out there and that is sounds lovely but with the DIY version we were simply able to do things properly without ever caring about how much it would cost. Add in better chassis design, far better PCB layout, better parts and we have a winner. 
