Yep, I have a 50 watt JCM 800. It's one of the loudest amps I've ever played through. The thing with Marshall's is that you have to crank them loud to get the sweet sound they are famous for, and cranking a 100 watt head to that level could cause permanent hearing damage. My 50 watt head cranked up to about 7 will make your ears ring for a while.....

Although I've never used the power break, I've heard people say they shorten the life of the tubes in the amp. Don't hold me to that though, just what I've heard.

Overall, the best sounding JCM 800's to my ears are the ones built in '84 or earlier, although mine is an '87. The re-issue "new" JCM 800's just don't sound like the older ones, they just sound like a new model from Marshall to me.

My 2 main guitars are a Music Man EVH (stock pups) and a Gibson SG (Dimarzio Tone Zone in the bridge) through my 800. Both guitars have about the same output (pickup output). I keep the gain set between 7 and 8 and the volume around 7. That's the "sweet spot" setting for me. Lots of sustain without too much gain. Too much gain muddy's up the tone.