Hey man not to sure all that your using in your rig, and how you'll be controlling things from the out side But I suggest a Ampete 222. You can find Pete Thorn demos on the tube, its perfect for a two head system. I use a tc electronics g system so I have midi and relays all covered. I used to do all my head switching with a Radial headbone bone but found there are problems resulting with running high gain amplification. Also you need a two loop switcher for your effects loop. What's cool with the 222 is it covers amps input, speaker output, and effects loop.
Somthing to consider, but I'm not sure that you can run both heads at once. I think it's just switching between heads and two cabs. Good luck man!