that's what The Beatles did Shea Stadium with innit?
But seriously, I think that for the actual sound to catch up with the potential for greatly improved sound, then people may need to adhere to one basic principle; don't be too loud on-stage. The majority of Backline Amps are designed to work a whole room on their own, not to be reinforced w/ f.o.h. or monitors, but it's not very Rock n Roll turning up at a gig w/ a 1U pre-amp as opposed to 16 AC30s (Brian May) or 5 Ampegs (Bootsy Collins). Also, from a guitarists' p.o.v. the Amp set to 11 is part of the sound (ala Hendrix) so I think that the advances made by P.A companies could have been held back by huge guitar amps in multiples. (GET A POWER SOAK, SAVE YOUR EARS AND SOUND BETTER!?)