I've had my K702's long enough to have burned-in at least a couple hundred hours. Pretty early on in the burn-in time, I put them on and felt I could hear a pretty noticeable difference had occurred. I would describe it as having developed a creamy quality. I realize that's kind of nebulous, but suffice it to say it's a good thing.
About a week ago, the Woo WA6 arrived. I'm running it from my computer via usb to a HeadRoom Micro DAC to the WA6. I am new to this headphone game, so I picked the Micro because it had optical, usb, and coaxial inputs. Many others don't offer all three. It's very compact, truly a space saver. I have no idea if it has "synergy" as compared to some other combination.
This set up sounds awesome to me. For example, on Santana's "Supernatural" in DVD Audio, there is a song featuring Everlast called "Put Your Lights On". The acoustic guitar intro chords have the sweetest, most three dimensional sound and the vocals are so detailed and natural. The whole album sounds amazing. I would say this set up sounds pretty amazing with anything I put through it. But there are certain sounds that really stand out. Acoustic instruments, in particular, really shine. Electronic sounds are great too, though. On a trance song called "Cloudwalker", at one point there appears these spiraling electronic squiggles. They sound like they're hanging from the ceiling about 5 feet in front of you. It's very cool. I'll say that you can really tell which recordings were done technically well. I now understand very clearly about the quality of the source issue. It's not that an average recording sounds bad. It's more that a superb recording is mind-blowing. Another thing I'd say is that less busy recordings sound better to me, in general. What I mean by that is recordings wherein not every inch of sonic space is occupied by some sound.
The last thing I'll comment on is comfort. I don't find them to be very comfortable. The leather band that trapezes across the top of your head is very hard and presses against your noggin. Yeah, it's leather. It'll outlast me. But I'd rather have something pliable, soft and breathable resting on my head. Also, the ear pads aren't very soft. What I do like is that your ears can roam free inside them as there's a ton of space. I feel like comfort should be a foregone conclusion at this point in the evolution of headphone design. They should sit on your head and envelope your ears in a virtually un-noticeable manner. I don't know why they couldn't have made the earcups out of the squishy/jel-like/foam. It would conform to your head more easily and be much softer. Maybe it detracts from the sound somehow.
All in all, I'm very pleased with what I came up with. When I listen to a superior recording of some great music, it's audio ecstacy