I should start this out by saying that I've only ever played through one 100W half stack: a H&K tri-amp or something like that. It was OK.

What I've been wondering about lately is what 100w amps are good for. Pretty much every amp I've ever owned has been too loud for me when I've turned it up to max -- if I ever even got there. I know sound is logarithmic or something, so that a doubling of volume requires 10x the wattage, but I guess I just don't understand the role of huge amps. Are they something you use when you want a lot of headroom? When you're playing outside and you don't have a powerful PA to mic the amp? When you want to feel your clothes flap around you? When you just want to feel like a rock star, playing in front of a huge amp?

I'm guessing the answer to the above questions is yes to all of them, but doing that would miss the point. I'm curious what the primary motivation is for using big amp heads. I notice a lot of pros use them, and a lot of the time they use three 100w amps (Mayer, Bonamassa, etc.). Certainly there must be some reason they use three amps, right? They're playing mostly venues with as much PA as they need, and oftentimes I think they even use isolation boxes, so what is it that those giant amps give you that little ones don't?

I think I've fleshed out this question enough by this point, so hopefully someone has some knowledge about it. Thanks!