Canes, the 600 goes about 10Hz lower than the 500. I won't have mine for another month. But its performance would be somewhat equal to my 800. It just can't go as loud. That 10Hz doesn't sound like much but it makes a tactile difference and renders the bass more transparent and room-filling.

Have you tried the linear/boost switch yet?

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