I heard them BRIEFLY (I was pretty convinced the XA series was for me, but I wanted to at least remain open minded). I really liked both the X250.5 and 350.5. I thought the bass was a pinch better on the 350.5, but honestly it was close. I thought the 350.5 had better dynamics and little wider soundstage.
For me, it came down to xa160.5, xa200.5 and x1000.5. I was oh so tempted to go for the x1000.5....but I felt the xa160.5 was a perfect match for my Sonus Faber speakers. It sounded so balanced from top to bottom.
Don't fret - the x250.5 is outstanding - Nelson Pass is a genius!
Mike