They don't begin clipping, they begin transitioning from their set bias point. The XA30.5 starts transitioning from Class A bias at about 40 wpc @ 8 ohms, that's when the meter starts moving. It doesn't clip until about 130 wpc @ 8 ohms IIRC. Why I even bother clarifying any of this is beyond me, bored I guess. You could just buy good amps and avoid all this meter nonsense.