Frankg,
I could be mistaken, but I thought he said "best period". After that comment he mentioned that he personally owns the X350.5. That is what lead me to believe he thought it was the best sounding Pass amp. I would audition both and take home the winner.
It really is a difficult question for a manufacturer or a dealer to answer. If they say the X350.5 is better who in their right mind will buy the more expensive XA160 i.e. if the X350.5 does indeed sound better.