For HT I've become a fan of Aerial loudspeakers. They play loud and clean with good punch, and will provide excellent treble without getting harsh. You could run up front LR3/CC3B/LR3 (2x7", 1x5", 1x1" driver configuration), and for the sides and rears a combination of SR3s or LR3s. Not cheap at 1.5k each. If your budget allowed Aerial's new LR5/CC5/LR5 up front would easily pressurize your large room, but you may need more power.
