Welcome. As mentioned the KC06A are better than Havi.
Now here is the difference between the two KC06 and KC06A.
Both KC06 and KC06A deliver with a top notch performance! Starting with KC06, Is a very well balanced sound with a touch of mid-centric brightness. Starting with a bass, you get a great quality with a detailed performance. Can clearly hear separation of sub-bass and mid-bass, but sub-bass quantity is just there to give sound a body rather than a rumbling to make you feel it. Mid-bass punch is snappy and quite satisfying. The bass feels a step above of the reference performance, and it's pleasantly well controlled within it's frequency range. Mids are very detailed, clear, slightly upfront but still in great balance with the rest of the sound. Their performance translates into great vocal delivery, very organic, with a touch of brightness, but still smooth. Treble is well extended, detailed, with enough brightness without being too overwhelming, and still very easy on your ears. For the comparison, if I consider RE400 to have warm reference sound, KC06 has a balanced reference sound.
Now, the KC06A kicks it up a notch into a direction of a more commercial sound signature with a slight v-shape cut (relative to KC06). Luckily, they did it a smart way without doing any extreme tuning to kill the mids which sounds a bit warmer in comparison to KC06. The bass here gets a refreshed quantity of rumbling sub-bass that can even put a smile on some bassheads. You still get a great separation between sub and mid bass where the later one is on par with KC06 performance. Bass is still well controlled without spilling into lower mids or the rest of frequency range. Mids are still detailed but now just a bit recessed to bring up a power of the low end. Ostry didn't reduce the quality of the mids except for smoothing out some brighter peaks, and just slightly scaled down the quantity while keeping most of the original attributes from KC06. Treble is still well extended, has a similar crisp performance without any hint of sibilance. Also, don't find any significant difference in sound-stage width. A principal change from KC06 and KC06A is enhanced/additional sub-bass and slightly recessed warmer mids.
Now, when it comes to ergonomics of the design and it's comfortable fitment and the sound signature - both KC06 and KC06A are identical that can be worn over the year or under.
Most importantly the KC06A that is off Massdrop has a revised cable since it's newer and people have reported it failing and oxygenating causing a green color that's visible and this will eventually cause a breakage in the line. The original KC06 did not and do not have this issue. I purchased mine off Amazon from SHENZHENAUDIO for $46.00
Hope that helps.