Be careful when you take advice from people.
Playing doom, thrash or death means you care- and thoughtlessly expose yourself to volume levels that some users here on the forum would react to by turning around and walking (running) from the room.
I know for sure that my 'loud' is not their 'loud' and I'd wager that your 'loud' is closer to mine than theirs.
Doing what you do with a 2x12 cabinet works, but only if you have some elite 212 super cabinet like a Barefaced twin and lots of power feeding it. I did play doom with an Aguilar GS 212 - which is not a bad cab at all - but it simply did not cut it. Not even close.
So if we're talking about regular cabinets, a good 410 is minimum but 215, 412, 610 or 810 are much better suited.
When you want to have a grindy, big low end, you need do move insane amounts of air. Especially when you tune down or use a 5 or 6 string. Set up against a hard hitting drummer and a guitar halfstack with 412, you need some capacity behind you. With not enough cabinet, the only safe bet is to Lemmy Kilmister it and simply dime everything except for bass and treble, which get turned off completely - but that won't really work with Orange amps as far as I know.