PPIMV's really suck on 4 hoke Marshals and any amp that gets power section distortion. They also mess with the NFB and presence controls. I ended up removing them from almost every amp I have tried them in.
I would suggest the JohnH or Formal Lotus if you want an actual attenuator. They don't mess with the frequency response like almost everything else on the market.
If you want a reactive load and re-amp solution, I would consider...
- The PS-2 or PS-100 (OK load, built in tube amp, some nice features)
- The new Two Notes (appears to be better load, built in IcePower amp)
- Suhr RL and separate power amp (Good load, flexible power options but not integrated in one box)