Well, you certainly can but don't expect any major differences. Assuming your computer's audio chip is competently implemented, and the source material isn't mastered by idiots, the limitations of 48000hz/16bit are generally considered below the threshold of even best-case frequency range of human hearing, and most adults are well below that. Some people claim windows's resampler can audibly degrade quality, I don't personally hear it but my hearing tops out around 13KHz, YMMV.

I'm not aware that Windows lets you see this directly.

Unless they are outputting in "exclusive mode" all your programs' audio output goes through the windows mixer. Windows sound settings -> device properties -> additional device properties -> advanced -> default format will let you change the default sample rate/bit depth of the windows mixer, out of what Windows detects your audio hardware supports.

If you're paranoid, you can use a player that supports outputting in exclusive mode. That should in theory send bit-perfect output from the app to your audio hardware, but as the name suggests, only that app gets to output sound, which may cause various issues when other programs try to do so.

the biggest upgrade you can make to any pair of headphones is being able to use a parametric equalizer (if you happen to mainly listen on a pc, this upgrade is as easy and free as installing equalizerAPO).

Probably not, but peace of mind is worth something. If it's not noisy, I wouldn't bother, that's the main problem with computer audio outputs in my experience.

"last high end headphones" haha yeah sure

congrats!

Sure, it's a little unusual with modern recordings but there's no law that says a recording's stereo mix has to be balanced. Albums are usually mixed on loudspeakers, where such imbalances are less audible since you don't have full seperation of the channels.

Yes, you need a seal to not leak bass, though the HD600s aren't that sensitive to it IME, as long as it is more-or-less in full contact with your head. Pads generally have a pretty considerable effect on sound signature, and if they are replacements/old worn out ones it would definitely have some effect.

What source were you feeding it before?

Really doubt it has anything to do with that DAC, unless it's defective and has some nasty high audio frequency oscillation for some reason.

K702 does have some pretty large treble peaks above >10Khz according to various measurements but it would be strange if it took a new DAC to make them troublesome.

as long as your source is capable of driving your headphones without major frequency response changes (ie, Sennheisers and OTL tube amps) that is very normal, because the differences between competently designed sources are below the threshold of audibility. fortunately for snake oil salesmen, the human auditory system is very adept at imagining differences.

I think you could get them to sound very close to each other in terms of their broad tonal signature, but the devil's in the details, which show up as those little narrowband wiggles in the FR plot. For the most part that stuff is simply not amenable to correction via EQ. The Utopia and Clear may be similar, but the drivers are made of different materials, they probably differ in the finer points of their driver/enclosure design. Some driver distortion mode may very well show up in an FR, but you can't really fix it without fixing the driver - at best you could reduce whatever frequency excites that distortion, thereby probably doing more damage to the sound.

Well, except the FR is not the same at all. I'd expect the overall tonal signature to be be fairly close, but all those little squiggles are audible qualities of the sound, with some fairly low-Q >3dB differences exactly where your ear is most sensitive.

But what are you going to do about it, have some kind of EQ with dozens of high-Q filters that would be completely different on your particular cans/ear or even headphone seating? Ultimately the FR measurement is only useful to a point.

I think the vast majority of what people describe as "technicalities" are just facts about a headphone's frequency response, as perceived at the eardrum, and colored by non-audible qualities that feed into one's perceptions, like price. But that doesn't mean that these differences are, realistically, measurable or correctable. FR measured on a test rig with a plastic ear is useful to a point but very much secondary to how it sounds filtering through your ears and sensory system.