I think that Yamaha did well by not installing PX3 amps inside their MX-A5000\/5200 11ch amps. Those pro amps have quite inferior specs than any of their audiophile power amps.\nIMO, the Crown XLS 1502 and the Yamaha PX3 are adequate as Class D subwoofer amplifiers but their high THD figures with either no published frequency range or limited to the frequency of 1 kHz only don't inspire much trust as to their overall performance as high fidelity amplifiers.\nHave you ever DBX'd them to see if there's an audible issue? Because I'd wager decent money that there isn't. \n\nCrown's intermodulation distortion figure of <0.3% is not acceptable for hi-fi or studio playback. Yamaha doesn't even publish their IM figures in their specs. Shame on Yamaha!\nLow-frequency distortion from a subwoofer or wide-range speaker with music signals is undetectable until it reaches gross levels approaching or exceeding the music playback levels. Only in the midrange does our hearing threshold for distortion detection become more acute. For detecting distortion at levels of less than 10%, the test frequencies had to be greater than 500 Hz. At 40 Hz, listeners accepted 100% distortion before they complained. The noise test tones had to reach 8,000 Hz and above before 1% distortion became audible, such is the masking effect of music. Anecdotal reports of listeners' ability to hear low frequency distortion with music programming are unsupported by tests, at least until the distortion meets or exceeds the actual music playback level. These results indicate that the what frequency it occurs is at least as important as the how much or overall level of distortion. \n\nI'd love to see where you are drawing your "what's an acceptable value" opinion from.