Right. The THD, even though I know it's there, is not objectionable except at around 20Hz where I can clerly hear chuffing. In real-world listening situations, this chuffing doesn't even enter into the equation. Once in a while, I'll be able to locate the sub during a movie explosion but this is no big deal.

BTW, these graphs show output below 16Hz. My 600 is totally silent below 16Hz. I can hear 16Hz (or artifacts thereof) but at 15Hz there's nothing.

House of the Rising Sone
Out in the mid or far field
Dedicated mid-woofers are over-rated