I looked at the Captor / Captor X when I was looking at loadbox/attenuators. FWIW, I like my poweramp to be a big contributor to my sound, which means louder than I want it to be.
It seems to me the Captor / Captor X is great if you want to go direct into an audio interface / use IRs; i.e., the speaker sims. which I didn't want.
with any loadbox rated for 100W, I'd be careful because many tube amps can exceed their stated watts at peak. IIRC, there are a few that are rated at 150W+ Fryette?
FWIW, I had one of the first Torpedo CABs in North America, I preordered one before they were released so I'm not anti-Two Notes...
What I want in a loadbox / attenuator is the sound of my amp at any settings into my cabs; with the ability to control the actual output level. The closest thing I found was the Koch Loadbox II Power Attenuator, DI Box and Speaker Emulator.
In the end, I didn't buy anything; I just use ear protection and play louder than I should.