Re: using two DSP'd centers plus a LFR. I know the picture above showing the back of the unit is of the prototype, but I don't imagine it's going to be any wider, and that back panel looks pretty crowded. With a little squeezing I can see how another single input/output could be added for a center, but two might be pushing it.
But as long as the centers are matched there's no need for two separate DSP filters, the output can be split with a Y, and that run to the inputs of two individual amp channels.
Pioneer VSX-1018AH-K, PDP-5020FD, DV-79AVi
Axiom M22s, VP150, QS8s
Sony PS3, surround backs