I have always felt the Ecstasy had plenty of gain. For reference, what is your idea of a modern high gain amp?
Of the ones I've actually played? Dual Rectifer (barely), 5150 and derivatives, Diezel VH4 Channel 3 and 4, Diezel Herbert, Framus Cobra, Bogner Uberschall, VHT/Fryette Ultra Lead and Deliverance, Rivera K-Tre, Hiwatt Super-Hi, most KSR amps, maybe some Engls, some Randalls (Thrasher and Satan), some Laney amps (the Ironheart series), etc. There are tons of more recent high-gain amps that I'm sure fit the bill. But I've not personally played them. Like Omega, Driftwood, Wizard Hellrazor, etc.
Then there are the diode clipping JMP/800 clones that can do modern metal with a boost (Cameron Jose, CCV, Fortin Meshuggah, etc.) and Wizard MTL, Silver Jub, etc.
Amps like the XTC, Shiva, SLO, many older Mark Series amps, H&K, and so on are absolutely high-gainers with great sounds. But I think many of them need a boost to deliver the goods for modern metal. Keep in mind "metal" goes all the way back to the early '70s. So can an XTC get enough gain for some Deep Purple or Alice in Chains or Bush or Metallica or Creed? Sure. But would it be a smart choice for modern day Meshuggah? I'm not convinced.
I just saw a video that came out today of someone doing "Drop C Chugs" on a Shiva. Sounds great. But again... not my idea of modern-day metal tones because it's still quite loose and ragged sounding and if it wasn't tuned to Drop C, it wouldn't sound nearly as heavy. There's a reason Tesseract, Periphery, Meshuggah, Jinjer, Monuments, Animals as Leaders, and so on don't use amps like the XTC...
Most modern metal bands are using modelers and profilers, not tube amps: Kemper, Fractal, Helix... or running clean amps as pedal platforms for high-gain sounds to stay clear for 7, 8. and 9-string guitars.
Right now, if I had to reach for a few tube amps for
modern-day "metal", they would be:
1. 5150 III
2. KSR of some sort
3. Hiwatt Super-Hi
4. Highly modified 800 with a boost
5. Diezel Herbert
6. Boosted Mesa Rectifier or newer Mark
But honestly, most bands are running Fractal or Helix live.