Of those 4, the Invader 2 is my least favorite. It’s more polished and processed sounding and smoother/less aggressive than the other 3 you listed. The Invader I has the tightest bottom end of those on channel 3 and sounds quite heavy, modern and scooped, big bottom end, but it’s also polished, smoother, not as growly and so imo not ideal for thrash and I wasn’t crazy about its other channels
The Inferno and Savage I think would work. The Savage will be tighter, stiffer, brighter, more upper mids and the Inferno has more low mid growl, warmth and I think much better for playing leads. I’d also consider the Artist Edition. It has a really great upper mid growl and is less compressed and processed sounding than the other Engls, but still has that kinda sound
For the kinda sound you’re describing under 2k, a Mesa/boogie mark iii would for sure be my pick and would be under 1k or maybe one of the earlier rectifiers. If you didn’t mention the scooped or clean part, I’d have also suggested an old jmp2203 or jcm800 with a good boost pedal
If you hunt around, you may be able to also find a used KSR or Revv amp under 2k. They’re also on the compressed, less organic side like the Engls, but also have lots of growl and can be very tight and not as compressed or synthetic as Engls to my ears, but still in that direction. If you’re super picky about a raw, organic like I am (which I think is important for thrash), I say get a mark iii, but it sounds like you’re on the right track if you only wanna look at Engls
Actually, maybe you can also find a Diezel VH2 used under 2k