My English is not good, sorry about that.
Prepare to laugh. Today i got my XS and i thought i was gonna be surprised by the sound quality. But i can't hear ANY difference between them. Same weak soundstage, same harsh treble, bass is almost non-existent.
I think the problem is because I don't have a dac/amp, so they are plugged directly into my pc (alc1220-vb). I use them on 100% volume but most of the time it's not loud enough. 990s were good at 70%. Do i really need an amp like Fiio K7 with balanced cable to make them sound at least better than the 990s...? Or all this will just make them louder? Please help :(
Thanks guys for helping me. Looks like the Fiio K7 is the best option - powerful and not too expensive. I'll get the dac tomorrow.
P.S as CPOx said, i spent more time listening to music with XS and yeah, even with my mobo i can hear the difference now. The soundstage and imaging is much better, the bass has somewhat of a texture (this wow'ed me), but still the treble is a bit too bright and often sibilant, just like with 990s.