Chuck Schuldiner

The Empty Words Project is founded by Chuck's family. Here they republish an interview with Pit Magazine, originally published in June/1999, Chuck Said: "My amp is a Marshall Valvestate head and cabinet, that's about it. I don't use effects except for a little chorus on my leads, I really like a basic setup." This article from Guitar Geek confirms this as an 8100 specifically.

During the "Human Tour of the World" in the early 90s, Chuck was miking up a Gallien-Krueger model GK-250 with hollow stacks for appearances. Aditional info: https://en.wikipedia.org/wiki/Chuck_Schuldiner

You can see the amp at 0:12

According to this rig diagram, Chuck used a Marshall Valvestate 4x12 cabinet.

At 00:54 into the video we can clearly see Chuck using a JCM 800 stack.

Chuck sitting in front of his Valvestate Cabs

In the YouTube video titled "Death - Iguanas, Tijuana, Mexico: Spiritual Healing Tour (October 6, 1990)," Chuck Schuldiner is seen using a Marshall JCM 800 2210 guitar amplifier head. The amp is clearly visible to his right, especially at the 1:00 mark.