Kevziek is right though, the meter on the XA series is just a "nice-to-have" feature and does not perform any function.
On the X.5 series, the meter, when it starts moving, indicates that bias on the amp is going from Class A to A/B operation.
My B&W N803s make the meter move on my X250.5.
Playing a recording with some decent bass/mid-bass, I have to get the preamp volume above the 10 o'clock position and the meter on the amp starts moving.
But I love the Class A operation of the X250.5 amplifier when listening on low levels. Plenty of drive, slam and detail.