Determining input power needed for Multi plus vs Quattro

I am looking at replacing my 24 volt Magnum MS4024PAE inverter with either two Victron Multi Plus 3000’s or one Quattro 5000 AND upgrading my 17kw Generac.

I have 4 Simpli-Phi batteries and I was wondering how much generator power does it take to charge my batteries and at the same time run an average 20 amp load to the house with either the Multi plus or the Quattro? Or what is the desirable amount of generator power? I have an older 17kw Generac and would like to upgrade it but I don’t feel I need 17kw.

I am thinking 10kw would be sufficient but not sure.