Yes, the oval pads bring everything out, if recorded materials had sibilant you'll spot it easily. There is no treble boost because is sound balanced over the spectrum, but coming from the original pads this will be considered bright, or treble boost. I like it this way because I can easy spot and monitor sibilance in the studio, but for casual listening the original pads will probably be better especially if you don't like sibilance. On the other way you can get the oval, and just add the 650s oval foam as a mod to rolloff the treble and add more bass.
Most of the today music is master at 0 db, this mean if you'll add any boost EQ this will consider digital distortion and eventually will add more random sibilance to your music
I'm getting more and more curious about these pads. And I've actually noticed that these headphones don't need the treble boost, it sounds really good at 0 db.
Extra foam mod is always an option for sibilance, so I think it will be fine.