That's a good analysis, John. I found out from Tom that this amp will provide 60W clean into 4 Ohms from 20Hz up (it's 3dB point is at 10Hz). We may therefore be able to play up to 107dB peaks for a total headroom of 20dB.

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