Stehno,
I think you can remove virtually all sibilance/distortion from digital. If you want to get technical and say absolutely 100% is not possible even with the best parts and designs, I could acknowledge that point. No playback system I've heard is the same as the real thing yet.
However, I feel confident saying that more removal is possible than most people think. Certainly, you can get it to the point of where it is reasonably negligible by today's standards and not causing fatigue or causing you to avoid certain hot recordings. See my recent review to see how I got rid of it.
One possible litmus test CD you can try is Charles Lloyd Canto. The first track is about 16 minutes long. Even if that type of music isn't your cup-of-tea, you should be able to listen for 16 minutes. If you're CDP and the rest of your system is up to par, you should be wanting to listen until completion. You may even be nodding your head or tapping your feat at the end. If something is wrong, it will quickly grow weary, fatiguing after no more than probably 9 minutes.
BTW, this track is also good for picking up low-level detail and testing system transparency. You will likely hear the performer breathe as he plays early-on. However, the difference is whether you occasionally hear the breath or you hear virtually every breath - deep and shallow. It's quite an excellent recording IMO.
