I have only found Koreisch so far, is there more of this? You know, like doom metal + grindcore in one.

Try Disembowelment. They play this unearthly kind of death/doom that goes between funeral dirge and near grindcore blasts. Also check out Prophecy Of Doom's debut album, although that one is a bit crustier.

also check out Inverloch they are a continuation of Disembowelment

Goatsblood. Sludge that gets grindy

http://www.youtube.com/watch?v=nGx4fXB1B4E

speaking of sludge/grind, Soilent green is another.

Cower plays powerviolence/doom. Powerviolence is quite close to grind sound wise.

Maybe a bit of Facedowninshit. they have that whole mix going for them. and yea actually just start investigating more into some PV. it's pretty much exactly that. doom/slude riffing with grind in short bursts.

give Low Places a shot as well.

Neon Hole might be up your alley. More sludge than doom but definitely worth a listen.
http://neonhole.bandcamp.com/album/neon ... plit-7inch