It would get expensive...

Maybe the amp and DSP could be shared between the speakers... only one more set of wires.

I guess the M60 and M80 are deep enough to have a 12" driver mounted on the side. Wouldn't the box need to be quite a bit bigger to support the sub ?

M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8