The other consideration is the sensitivity, aka dB per watt. For twin cabs wired parallel you add 6dB to the quoted sensitivity spec, hoping like hell it is honestly applying to the 70 to 140hz octave. Then you add 3dB for each doubling of 1w they can handle before power compression kicks in. 1 2 4 8 16 32 64 128...256 is stretching a little but what the heck, 8x. Add 24+6 = +30dB to the number Orange gives for 1 cab. Might pay to do some research on their veracity.
The Barefaced 12'' driver isn't so sensitive but eats up wattage. I believe they claim 97dB honest broadband sensitivity and 512W isn't a big stretch when rated to 600W. 97 plus 27 is 124dB. Barefaced come to 127dB so they are not allowing for power compression and even cribbing some extra mathematically speaking when they call it 800w in the Big Baby. Tbf they do call it Max ~dB which I guess it could do in a thump without breaking.
Super Twin is a smaller cab minus HF driver and gets 133dB ~ max output with 1200w so maybe ~130 with the Terror giving its all.