In the absence of a much needed 4 x SPDIF output card, I would prefer a one box AC12 to sit behind the processor, much like the AC11 in functionality. One additional power outlet, and it utilises all the current wiring.
Or better still, just get that 4 x SPDIF into production!
Cheers
George
My understanding is that the AC12 is in a half-width 1U sized box and that two of them can be mounted together in a 1U rack space. Four of them would be required for 7.1 DSP speakers with SPDIF/COMMS connections, so a 2U rack space would be required for a full DSP setup.