It's 210W @ 6 Ohms (unless you bought an older of the same model) but that spec isn't that meaningful frankly. You can expect around 100 clean watts for 2-channel and that should be plenty. I trust Onks - good buy!

Set to 6 Ohm. The 4 Ohm setting limits the output voltage and that's bad.

Bi-amping is an ok practice particularly since it's free. It's bi-wiring that isn't useful except in some systems.

Start by setting the cross-over to 80Hz.

Have fun tweaking.

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