One of the keys to what makes Klipsch earphones good is the angle of the earphones' post (what the eartip attaches to) and the conical shape of the silicone eartips, of which four sizes come included. The combination creates a comfortable fit and Klipsch arguably makes the best-designed silicone eartips, giving a tight seal, which is crucial for maximizing bass response.
Comparing the X7is with the S4 IIis, I found the X7i earphones had cleaner, more detailed sound, with slightly tighter bass. Again, neither of these models really pumps out the bass the way the V-Moda Remix earphones do, for example, so if you're a bass lover, you'll probably be disappointed.
I liked the sound of the X7i. Similar to the S4 IIi's sound, it's well-balanced and pleasant -- but clearer at the same time. I also found the earphones comfortable to wear for long periods.
My only problem with the X7i earphones is that when you get into earphones that cost more than $150, you start expecting a lot, and they didn't deliver quite as much as I was hoping. They're quite decent, but I was just left wanting a little more; for the money, they could have been a touch more dynamic and little bit more open.
If you've read this far, you've probably noticed I have mixed emotions about the X7i earphones. On the one hand, they're very slick-looking noise-isolating in-ear headphones that are comfortable to wear -- and they sound good. But if you came to me and asked whether you should buy this over the S4i II or another $100 model, I'd have some reservations.
The Moshi Keramo earphones, which also feature ceramic earpieces, offer similar sound for around $120, though they're arguably not quite as comfortable. And there are plenty of other options in the $50-to-$150 range, including the Phonak Audeo Perfect Fit Earphones PFE 022 + Mic.
The long and short of it is that the Klipsch Image X7i earphones are a very good in-ear model that would be easier to fully recommend if they cost about $50 to $75 less. If you find them for that price, they're certainly worth considering.