At the moment there is no version of the PM60/90 with a passive XO between the LF and MF/HF section. So you have to (at least) bi-amp the cab.
2x12NDL76-16 will give you 8 Ohm nominal when parallel.
1x DCX464-8/16 with a passive XO between the MF and HF will give you either 8 Ohm or 16 Ohm nominal.
So this means you need 2 amp and DSP channels per box. Regarding the passive XO for the DCX, I would look at the B&C FB464 or the blue aran offering. Of course you could also design one on you own if you have the ability.
2x12NDL76-16 will give you 8 Ohm nominal when parallel.
1x DCX464-8/16 with a passive XO between the MF and HF will give you either 8 Ohm or 16 Ohm nominal.
So this means you need 2 amp and DSP channels per box. Regarding the passive XO for the DCX, I would look at the B&C FB464 or the blue aran offering. Of course you could also design one on you own if you have the ability.