Peavey 5150
Krank Kranenstein
too modern IMO, except for Pantera sounds (Krankenstein)
i wouldn't even want a krankenstein for pantera... dime used SS Randalls in pantera... far as i'm concerned, as you say, the krank would be too modern for most of those tones, and not really sound like pantera anyway, in my opinion.
basically, for the tones in question (and as far as i'm aware):
black album metallica: mesa
testament: i think peterson used mesa, skolnick marshall? at least at one point.
COB: not to familiar, i think they're marshall? not certain.
Pantera: you'll probably struggle with tube to get that SS tightness, unless you go for something that's super-heavy and tight, like a powerball or similar... and then you lose out for the less heavy tones.
G n R: marshall.
Far as I can tell, you're probably going to have to make some kind of compromise... are you willing to compromise on the marshally tones, or the mesa-y ones?
also, are you willing to go second hand?