Pretty sure everything up to and including In Search of Truth was a Triaxis through a Peavey Classic 50/50 Poweramp. Tom confirmed in an interview just after ISOT was released that they used that setup, not sure if that applies to previous albums, but I assume so. And I always thought Recreation Day was a 5150, but recorded at Fredman hence maybe why it doesn't sound like a traditional 5150 tone. I'm pretty sure the last two albums were a 5150 as well. The live album was a 5150 boosted sometimes with a DS-1 (mainly for leads).
Overall their tone just plain kicks ass. Especially on the DVD (where it looks like Henrik in particular never picks that hard, yet the resulting tone is really agressive), I'd love to have a tone like that, so thick and tight, and they don't use a TS or anything for rhythm tones as far as I know.
I've got the settings off I think it was Henrik's 5150 on the Gear Talk section of the DVD, I'll post them later if anyones interested in trying them out?