Even if the actual designer can make the crossover, he has to physically measure your room response using at least 1/12th octave FFT analyzer. If not , he has to know your room dimensions, materials of your room. listening position and so forth. 8 f113's would be great stacked with each other. It would be a time consuming work to align everything taking into consideration the latency introduced by digital processors. Have identical subs, do not mix models even with the same manufacturer. A seller will sell you 50 subs and tell you its better to have that number. In the case of concert halls involving large area acoustics, the more subs the merrier!
With regards to your Center channel, I strongly believe that a much better sound would be achieved by using just 1 center channel. It is precisely what you said that a Y connector was used as the input for tha amps running the centers. In effect, they are in mono configuration not discrete. The timing difference of each driver from each enclosure caused comb filtering.
It seems that the evidence uses symmetrical drivers which is true but they don't use the same crossovers. It has a 5way design crossing at 300,500,2.3k and 8k. I would suspect that 300hz is the cutoff for the woofers and each driver (low mid, high mid, low tweeter and high tweeter) uses those mentioned frequencies. They don't work with the same cut off frequencies. If they do, comb filtering would occur. In the case od the woofers working below 300 hertz, the cancellation and augmentation effect would smoothen the overall response of the low frequencies.
