A clipped waveform is by definition distorted. So before the amp starts clipping in the least there's a 0.016% THD. The while the clipping may not be hugely detrimental at 135 Watts, it has increased the distortion level to 1%.

From Wikipedia on Clipping:
"Clipping is a form of waveform distortion that occurs when an amplifier is overdriven, which happens through attempts to increase the voltage or current beyond its maximum power capability. Driving an amplifier into clipping causes it to put out power in excess of its published ratings, which are customarily done with a "clean" sine wave signal just at the onset of clipping."

Pioneer PDP-5020FD, Marantz SR6011
Axiom M5HP, VP160HP, QS8
Sony PS4, surround backs
-Chris