BobL,

It's also a matter of weight. Physics, as always, isn't on our side here. The better the amp, the more power it will trash as heat, so the bigger and heavier power supply you'd need. The better the speaker, the larger and heavier again it has to be. And guess who's gonna move the boxes day after day.

The bad thing about lightweight equipment, on the other hand, is that while walking toward the sound source you start hearing ugly distortions long before you can figure out as much as it's music being played. Not a good way to greet your potential audience, I'd say.