Great tones and reviews. You can't go wrong with a JCM800. I played it only once, poweramp gain was 5 it's was overwhelming the drums in the studio. Unbearable as you mentioned! and the gain, even boosted with a SD1, was not that high....the only thing I could add is, if... You're going to a loadbox, then there's the option of the Studio SC20 much cheaper. You'll still need the load box either way but JCM tones are there I think.
Hey man, Absolutely you can't go wrong with using any JCM800 amp, only thing that I will say using the studio classic amps compared to the bigger ones is that the don't have the same low end and sound bit smaller than the originals due to different transformers and the lower wattage.