i tried Sonus Faber EA1 last week, driving by YBA passion 100. i also have a Krell KAV-300i integrated amp for comparision purpose.
the conclusion i made is YBA still works best with transparent type of speakers like trangle/vienna acoustic/jm lab. the nature of YBA sound is not meant to be transparent. when drives an warm/thick sounding speaker like sonus faber, it makes the sound even more thick, dark and less dynamic. Krell KAV-300i, which is typical transparent amp to me, drives Sonus Faber better in this senario. however when KAV-300i, drives triangle speaker, it makes the sound too bright and harsh which basically makes the bright speaker too bright.
of course the bass of Sonus Faber EA1 is another story. so far i havent heard any better bass from a bookshelf speaker.