I think CK100Pro would be a fine replacement as long as you can tolerate some of what I feel is its "shortcomings" compared to CK10 -- For one, it suffers from a slight midbass hump -- Nothing too disturbing, but this is definitely a departure from CK10's ultra-linear bass, although as a trade-off, CK100Pro does have better low-end extension.
Regarding the treble tilt, CK100Pro shares CK10's familiar peak around 9k-10k region, but in CK100Pro's case the peak is much worse -- Not necessarily a bad thing, the peak does help with the perceived clarity and energy of CK100Pro -- But it might be disturbing for some. Then again if you are used to CK10 it shouldn't pose much of a problem.
Oh, and the biggest turn-off for me personally is comfort -- Gone is the tiny, disappear-in-your-ears shape of CK10 and CK100, and in comes the weird and clunky shape of CK100Pro -- AND SERIOUSLY WHAT'S WITH THE REVERSED, INCOMPATIBLE-WITH-OTHERS MMCX CONNECTOR? As far as I know only CK100Pro uses that kind of reversed MMCX connection; AT's insistence on using exclusive cable connection is still baffling to me.
But as Omnirai said, technicality wise CK100Pro is one fine IEM -- Clarity, Transient Speed, Instrument Separation are all excellent. And it really is well-built -- It feels like a $400+ IEM to the touch. Again, if you can tolerate the aforementioned shortcomings compared to CK10, you'll be hard-pressed to find better replacement for your CK10.
However, just to keep things interesting, I'd suggest j-phonic k2 sp - It's a well-tuned technically superb IEM with great top-to-bottom extension (for dual driver set-up), damn neutral and gobs of detail. It disappears in your ears too -- I'd say it's as comfortable as CK10 -- Not to mention that it's similarly priced to CK100Pro. One problem though; it's not widely available and you do have to go through a lot of effort to get it.
(Oh, and do note that opinions above is of course, personal, and what I heard is not necessarily what you might hear!)
