I've always understood "timbre" to refer to a realistic portrayal of that particular combination/permutation of tones and overtones that makes one instrument sound different from another, so that we can distinguish between a Gibson and a Fender or a violin and a viola. Tone can refer to a fundamental, and also to shadings of the sound: dull, bright, etc.
Timbre is also crucial to me. Though I'm also a sucker for soundstage. Width seems fairly easily achievable, but depth really adds something for me. And then that ineffable something that makes it come together and move you.