For me, it's dynamics, "that old midrange magic", dynamics, smooth treble, dynamics, a bass that breathes (rather than "tight" bass), dynamics, coherence and dynamics. A speaker without proper dynamics just can't get my blood flowing, no matter how well it does everything else.
Speakers: What's MOST important to you?...
When you demo a pair of speakers, what criteria do you use to judge the quality of sound? What must the speaker have or do that will bring out the check book or credit card?