I was in a sort of similar situation, also doom and death with a loud guitar player and blew up a 15" speaker. I got me an Ampeg SVT stack, 300 watt tube head with a matching 800watt 8x10. Preamp full, power around 5 or 6, it's enough for me. I do second the question about the drums, can you hear those at all? Because after my power move, we really had trouble hearing the kick drum. So we toned down a tiny bit and carved our eq to let it come through more (and told the drummer to get new skins).
gray makes excellent points here. As a sound guy who has mixed lots of VERY loud bands, I’ll amplify the advice re drums - none of those bands buried the drums. Good loud bands know how to divide up the sonic real estate for maximum impact.
Obviously neither you or your guitarist are going to be quiet but there is a “sweet spot” for loud and it may not be what you might think it is
Like, would blood have to be pouring out of his ears, or something (his brain, perhaps)?