Great band - I have all of their albums, fact fans. I even went to fucking Poland to buy them! (Well, not quite, but while I was there I filled my boots with metal )
It all depends on what you mean by heavy. If you mean quick, brutal, well, there are a fucking dozen bands that push past my acceptable envelope. What are they called ? I couldn't tell you because once they're too heavy for my tastes I couldn't give two flying shits about them.
Now oppressive atmosphere, and that feeling that makes you want to make the "claw of anguish" hand gesture while you listen to it ?
Well, fuck, stuff like Crowbar, Runemagick et. al. is Heavy in that respect