Ok, I'm going to get my first tube amp soon ( a Marshall jcm 2000 dsl head) but i'm not sure what amp cabinet to get. I was recommended this head from my guitar teacher A.J. Minette (from Human abstract, what he used for Nocturne) but he just said to get a marshal cab. Long story short i'm not sure which marshal cab to get, or even if i should get a marshall cab at all and instead get something else. I'm going to get the head used, and i won't have to much left over for the cab since i'm gonna need a tube screamer as well.

So TLDR... Amp cab for under $450 (american) used is fine, for metal, prog metal.

you could try craigslist. in my area i see them all the time for 300 used
Well, Jesus Christ, I'm not scared to die,

I'm a little bit scared of what comes after

Do I get the gold chariot?

Do I float through the ceiling?
I'd have to say, at that budget, go for a Marshall 1960A cab.

Done deal.

There are better out there, say, an Avatar with Scumbacks, or even an oversize Mesa, but that's more opinion than anything.

The Marshall wil be "standard".

You could ask a guitar store (not gC or sam ash) with a decent inventory of cabs, if you could bring in your head and guitar and try a few.

There's a shop near me that let me do this, but I know them pretty well, so YMMV.
Check craigslist for a 1960A or B...

or if you decide to go with something besides marshall...check out mesa, orange, avatar, framus, etc....something with V30s would be perfect.