Just curious Mav' : are you using the standard JRC opamps in your O2 ?

Of course! How could you improve on perfection?! Are you some sort of crackpot audiophool?? 

Bigshot thinks so:

http://www.head-fi.org/t/689409/do-all-dacs-sound-the-same#post_9963109

here as well:
http://www.head-fi.org/t/560122/all-dacs-sound-the-same

Even Bigshot isn't going to say that putting a crappy tube buffer into a DAC won't change it's sound when it can add clearly measurable distortion above know thresholds for audibility.

He'd certainly claim that they all should sound the same for philosophical reasons and that anything that doesn't is "broken".  I prefer transparent gear for myself, but I wouldn't go so far as to say anything else is broken.

People absolutely say that. People like the AudioCritic believe that any properly designed amplifier that is not actively clipping will sound indistinguishable from any other amplifier, and the only possibly difference will be if you purposefully introduce a form of distortion via something like 300Bs.

"The principal determinants of sound quality in your listening room, given the limitations of a particular recording, are the loudspeakers—not the electronics, not the cables, not anything else. This is so fundamental that I still can’t understand why it hasn’t filtered down to the lowest levels of the audio community. The melancholy truth is that a new amplifier will not change your audio life. It may, or may not, effect a very small improvement (usually not unless your old amplifier was badly designed), but the basic sound of your system will remain the same. Only a better loudspeaker can change that. My best guess as to why the loudspeaker-comes-first principle has not prevailed in the audiophile world is that a new pair of loudspeakers tends to present a problem in interior decoration. Swapping amplifiers is so much simpler, not to mention spouse-friendlier, and the initial level of anticipation is just as high, before the eventual letdown (or denial thereof)."

Emphasis added.

You left out some important qualifiers.  I would mostly agree with that statement but it leaves out the fact that many things do sound different because you can always screw something up or make something less than transparent intentionally.  Some people like that just because it's different.  Sometimes those flaws counteract flaws in other equipment you're using it with.

I used to like my Crack better than the solid state amp I had at the time but eventually I got board of it's added coloration and went back to solid state.  I wasn't wrong then and I not wrong now because they're just preferences.  Some people do call out others on that and I think it's wrong.  Preferring a colored amp isn't any different that preferring a colored headphone and calling other out on that is even rarer and even more screwed up.

Heck, even when we do such a test as we did with the Magni versus the O2 years ago, people just CHOOSE to not accept it or believe it. Data has a value even if you choose to disregard it or mitigate it's significance. Perhaps even more so in some cases.

Got a link?

Remember, next time you take cars for a test drive, make sure to do it blindfolded otherwise it'll be 'worthless'. 

That's a completely different thing Anax.  Unless you're only ever going to race it buying a car is almost always more about things like style, ergonomics, and comfort rather than just raw performance.  That would be like advocating buying a car base solely on the Sig's laptime or something.  You've actually got to live it, no matter it's performance, and I'll certainly admit that the O2 falls on it's face in regards to ergonomics.

Just curious Mav' : are you using the standard JRC opamps in your O2 ?

Yup.  Never bothered rolling because it sounds fine the way it is and I never heard a difference when I rolled opamps in previous amps I owned.

If you are set on the speakers you want, then the DAC and the Amp become the determining factors.

If you are set on the DAC and the Amp you want, then the transducers become the determining factors.

Cables proly, if you are set on the DAC, Amp and speakers. But IMO hard to fuck those up real bad.

Now, I think transducers are harder to get consistent and right. So I would start there. Though it be an iterative process where you find a transducer you absolutely must have, but has some special driving requirements which narrow your choices more that you would like, and it's back to the drawing board.

I think that's a reasonable assessment. If you can't hear a difference between a Martin Logan and a Magnepan, this might not be the hobby for you. I'd probably say the same thing if you can't hear a difference between a $500 amp and a $5K amp, both "properly designed," and not clipping, both with S/NR, THD, and IMD all below audible threshold. The differences won't be as large as the differences between speakers, but there WILL be differences. One pair of speakers vs. another is like comparing red vs. blue, not that hard. One amp vs. another is like comparing light red vs. dark red.

Cables are tricky, because IME, a lot of cables DO sound very similar, and some pricey cables don't sound any better than Monoprice stuff. Speakers and components I think can be compared using traditional sighted methods with notes, and you can then bring out the blindfolds if you're unsure of your initial findings.

Cables OTOH I think pretty much require blind testing in order to separate the wheat from the chaff. Cables also require at least a fair amount of critical listening skill, patience, and familiarity with recordings. I can pretty much guarantee you that any large scale ABX test using unfamiliar equipment with unfamiliar recordings using quick swaps will result in 50/50. The differences are just too granular to show up in that sort of environment.

Bigshot thinks the Hifiman RE262 and RE272 sound the same based on measurements. Nevermind he hasn't heard either of them, ever. Tells me all I need to know about his objective opinion.
http://www.head-fi.org/t/623043/cafe-sceptico-the-objectivist-cafe/330#post_9004942

2 well measuring amps: Cypherlabs Picollo (all discrete design) and ALO RX (new opamp model for iems)

At the time I owned both, I could play a particular song with some kind of recorded artifact around 30 seconds in. I could hear it on both but the RX pushed it very forward in the mix- at any volume- compared to the Picollo. So much so, I at first thought the RX was experiencing RF interference. Obviously it wasn't. The point is that no amp measurement, that I know of, can explain the way these 2 amps presented this recorded artifact. It would have been easy to distinguish these 2 amps in a blind test if I was given this particular song to use. Anecdotal perhaps but for me a glaring data point that all well measuring amps don't 'sound' the same. I won't even talk about one sounding leaner or brighter than the other, just that one made a specific moment in a song more easily detectable than the other.