I have sampled the CKR100.
I sadly did not get a chance to compare with the CKR90.
That said, as I have had the previous model, CKR 9 LTD and had extensive listening with the CKR 10, I feel I could give some thoughts of the new model.
Ergonomics:
The CKR100 is very easy to be placed in your ears unlike the previous model, CKR 9 LTD/10. It also feels like a legitimate 'premium' top class earphone when putting it in the ears.
In other words, it's comfortable.
This is so much of an upgrade from the original CKR9 LTD/10 series in which honestly, the ergonomics was horrible.
Size:
At first it looks pretty damn long. However, after seeing how well it fits in my ears, I guess this should not matter.
Sound:
This was a bit of a disappointment to be honest. Maybe this is why the new CKR series did not get as much rave in Head-Fi. Who knows.
The sound in comparison to the CKR9 Ltd... has not really changed much.
1. The bass is sharper on the CKR 100. Yay! But,... can't I just up the volume also in my previous model and get a similar effect?
2. The sound feels far more 'open' overall.
However, I felt overall it was more of a sidegrade in comparison to the old models CKR9 LTD/10 than an upgrade. The clarity was about similar and overall, I felt there weren't any noticeable improvements if any.
I felt that the pricing was mostly for the 'detachable' cables and the ergonomics and not really in improvements of the sound.
But I would add that it certainly feels like a 'premium' earphone unlike the original CKR series.
With all honestly, if you already own the previous CKR model (9 ltd/10), I just don't see the reasoning behind purchasing for the new CKR series as the sound is more or less very similar.
In fact, if you switch the CKR9 LTD earplug with something like a double or triple flange, the 'openness' sound is more or less the exact same to that of the CKR100 (surprising, right?).
So ya, I was disappointed with the new models.
That said, what did surprise me during the testing was the ATH LS200. While I felt the CKR series were better overall in sound quality, the strength of the bass in an 'armature' in the LS200 was unexpected. Though I have very limited experience with armatures, I must say that if I hadn't been told the LS200 was an armature, I would have expected it was a dynamic driver. In addition, the comfort was amazing like the new CKR series. This was a bit of a shock considering I really dislike over the ear types since most of those types ends up getting tangled up with my glasses.
However, at least in my opinion, if you already have the original CKR series, I just don't see the need for the new models. Unless you REALLY want better ergonomics, the extra cash could be saved. The new CKR100 feels more of the CKR9 Ltd sound repackaged into a better ergonomics earphone (and not much more to be quite frank).
If you are sold into detachable cables though, I would add it is still a great earphone. I don't know how it compares to the LS300 and LS400 but it still surely nice.
---Added---
Also do note that from this tier of IEMs, the sound quality is all top notch. I would compare the CKR100 favorably against IEMs like the Shure SE846 so while the CKR100 is not much of an improvement (I feel) from the CKR9 LTD/10, you also have to note that you are now getting closer to the edge of top universal IEM sounds. While the costs may leap a lot from here, the sound difference is very miniscule in the universal IEM world (or at least from the ones I tested).
<Honestly, I like the ergonomics of CKR100 far more than the SE846 anyways>
I still believe though that around 500, the CKR100 would probably be the best sounding of them all. After all, when the CKR9 LTD/10 was released, some listener in a site did post it as a favorite (the CKR10) as the 'best' IEM under 500. So ya, as of sound quality on all these high ends, it's top notch. I know my review seemed disappointed but I was also factoring in the cost. It is still a top class IEM. It's just that after a certain threshold, the sound improvements are not as noticeable at the top end of universals.
I have also checked other people's thoughts on the CKR90/100 series. Apparently, I am not alone on my opinion.
https://www.seeko.co.kr/zboard4/zboard.php?id=forum_etc2_1&no=153563
This person preferred the CKR9 (regular) to the 90 and 100. And in the thread, another listener agreed with him on that thought.
https://www.seeko.co.kr/zboard4/zboard.php?id=forum_etc2_1&no=151527
This person preferred the CKR90 to the CKR100 even though the price of the CKR100 was twice of CKR90.
http://blog.naver.com/ekdydehwlq/220965707006
This person preferred the CKR9 (regular) to the CKR90.
What these posts seem to imply is that just as I believe, the new models are more of a side grade in sound than upgrade. However, the new models are indeed detachables AND for once look/feel premium. It is honestly the most beautiful IEM i have seen without contest.