What Class D amp you are using for your woofers? (active system)

besides the power relation with sensitivity, the most important factor to consider for this application, is the amp's damping factor, is that right?

Damping factor and power cosmic. There is no reason to limit yourself to class D. Class D is popular for plate amplifiers because they can be made much smaller and produce little heat. But, if you are using passive woofers like I do I think AB amps are better. I use QSC PLX-3602's
3600 watts bridged into 4 ohms, Damping Factor 500. Now you also need a cross over. JL Audio makes an excellent one.