Have you made a decision on this yet? I have been considering the Shiva-X in a similar configuration as you are describing. I was thinking of two forward facing and two rear facing (firing against the wall). I was wondering what problems the rear firing woofers may cause as well. Any insight would be appreciated.Thanks.
Also along the way I have learned that to drivers sharing one box require less volume than two drivers with their own space,news to me but all good.
Also the cabinet vibration cancellation aspect is very appealing.
Just wondering about excess boundry gain (boom) with the rear facing drivers?
But one thing with the Shivas they seem to need twice thw power of the Peerless for any given volume.
Not that its a problem just a note