Unsurprisingly, the KC2 seems to be just a variant of K2. This is not necessarily a bad thing. After all, why would you change the formula when the formula works so damn good. The only difference between these two seems to be the design on the back of the housings. Also, I got ø5mm ear tips with the KC2, while ø4mm ones were included with the K2.
So, the review is literally a copy-paste. You may want to refer to K2's review for comparison.
First of all, change the ear tips to something more suitable. The included tips were definitely not made for these wide nozzles. I recommend using wide-bore tips, like the ones included with ROCK Zircon, or some of the whirlwind tips included with older KZ and Tennmak products. Fit and comfort with these earphones can change from one person to another, and it really depends on the size of your ears. People with smaller ears may find the bulky housings to be too large to fit in the ear, and will probably stick out. For me, the fit was quite good, but nothing like the amazing fit I get with earphones like TRN V80 and RevoNext QT2.
Lows / Bass
Once the ear tips are changed to some wide-bore ones, the bass gets quite extended and very pleasing. In fact, the bass quality and extension seems to be almost identical to RevoNext QT2, but just almost, as QT2's bass has more body, it is warmer and more energetic.
Mids / Vocals
Extremely similar to RevoNext QT2 and I could barely tell them apart. They are not recessed at all, but are also not edgy. The perceptional distance of voices and instruments from yourself is phenomenal. You will feel surrounded with sounds and will also be able to tell the direction from which the sounds originate. Not only that, the mids also sound extremely natural without any coloration, at least as far as I can hear. Those mids are as universal as it gets!
Highs / Treble
Also very similar to RevoNext QT2 and hardly distinguishable. Very detailed, crisp and sharp, but not fatiguing. Obviously, certain tracks (specifically under the electronic music umbrella) will still cause some pierce and it seems inevitable when it comes to bright earphones, especially those with balanced armatures located in the nozzles. However, those are some of the most extended and accurate-sounding highs I've ever heard so far. Certainly, you will get more sparkle with the extremely-extended treble of ZS6, but K2's highs will not tire you. Compared to the similar TRN V20, K2's treble is more accurate and detailed, less rolled-off but instances of pierce are far less likely to occur - and that what makes them truly worth their extra price.