I bought this to use with my Marshall SV20, since it is way too loud and doesn't have a master volume.
It's amazing to have so many options to attenuate your amp with quality without paying more than 500 euros. I feel like there is some minimal coloration on the sound, but I could be mistaken. Either way, I can get many amazing sounds on the amp while using this device.
The high cut option is noce, but I don't really like what happens to the "Marshall sound" when I use it.
I would also have liked to have more impedance options, because I don't find it worth it to pay double the price for the bigger Iron Man just to be able to use 16 Ohms.
All in all, I really love this piece of gear. I use this one for my Marshall cab and a Torpedo Captor 16 Ohm for my other cabs.