Most smaller to medium size venues in Tokyo already have a Marshall on stage. The 100 watt heads sound great through a 4x12 cabinet. I'll use any marshall 100 watt head they give me but I don't like the three channel heads (JCM 2000 TNS 100). I hate them because the effects loop doesn't work right. Some of my delays sound out of phase and there is always some sort of volume problem when using the loop. If I’m recording I won’t be using the loop anyways so they work fine for me. I just used a JCM 900 yesterday and it sounded great.
Dealing with volume: When I record, if I'm in any sort of decent studio, I can just put the amp in a booth and shut the door. If I stand in the big room, I might leave the booth door open a few inches which leads to all sorts of problems. But as I generally don’t do punch-ins or re-record my parts, it works out OK most of the time. I like Marshalls at 3.5 or 4. They start to sound woofy above that. The older ones didn't have a gain control so you just turned them up as loud as possible but the new ones have a gain control that I set at around 5 or so and I use something to boost my signal and sustain (I personally like Xotic’s BB pre-amp or their EP Booster). Check this video on how I get my tone:
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