Definately get more Carcass, specifically "Symphonies of Sickness". Fucking top goregrind.
Here's a few.
Death - the original death metal band (yes, I know that Possessed put out Seven Churches in '85, so fuck off). Get everything you can. If you're actually into buying albums, Utopia has Leprosy, Individual Thought Patterns and Human on sale for like $10 each.
Napalm Death - their stuff with Barney Greenway. I'd still recommend getting Scum and From Enslavement to Obliteration.
Bolt Thrower - Specifically War Master.
Cryptopsy (Even though their new shit will be terrible) - specifically "None So Vile". Phobophile has to be one of the catchiest death metal songs ever.
Atheist - All of their shit
Cynic - jazz-fusion/death metal, a great combination. Only put out "Focus", but it is one of the greatest albums ever produced.
Gorguts - I've only got "Obscura", but it has to be one of the strangest albums I have ever heard. In a good way, though.
Demilich - only put out one album back in '93, "Nespithe". Crazy time signatures, tempos and all that.
Origin. You'd probably like this, if you're looking for some intense shit played at ridiculous speeds.
Suffocation - specifically "Pierced from Within". Side note: I used this album cover as a related text for an English assessment, and got 14/15.)