I just want to say that I demoed the x20i today. I listened to it alongside every higher end model from shure and westone (same price bracket) as well as the RHA t20 and of course my not so trusty x10 (bought cheap, but falling apart. I have another pair which stopped working after just one year of use in the gym)
The short story is that the x20i blows away everything I heard from Shure, westone, and RHA. Its not even close. The smoothness of the overall frequency response from top to bottom simply doesnt exist anywhere else. Definitely not from westone or shure which had terrible peaky zones in the treble response and though the higher end models had a nice midbass response, there was a gaping hole in the sub bass regions most of the time and vocals somehow sounded hollow yet sibilant most of the time. Fitment was also far less comfortable, klipsch deserves an award for the level of comfort they provide vs the sound they can achieve with such a small package. It runs completely opposite to the 'huge unconfortable iem with multiple drivers' philosophy that shure and westone subscribe to. This is all in comparison to the x20 of course. On their own they're not bad, just not as good as the x20. Not even close
The x20 and x10,11,12 carry a similar sound signature, that klipsch smoothness you dont get anywhere else (those who appreciate it will know what i mean). The differences between them relate mostly to the amount of detail one can pick out as well as the quality of the upper mids and treble which is clearly superior to the x10 now..yet somehow retaining thay lovely smooth characteristic. The lower registers are roughly equal to the x10, but do sound cleaner thanks to the improved mid and top end
If you like the klipsch sound, demo these earphones if you can.
Have said all that , I did not buy them. They are very expensive, and my experience with the x10 raises doubts about build quality which the short 1 year warranty does nothing to ease. I really want them though. Maybe ill convince myself over time