As an update, I disposed of the Nuance 330's this morning. I moved twice, yet they served as my main system from 1995 to 2015, and were relegated to family room duty for the last 3 years. They were replaced with the Kanto Yumi active wireless bookshelf speaker in 2015, anchored by my Mirage PS12/90 subwoofer that I bought in 1994.
Soundwise, the Yumi's and the 330's are timbrally different, but similarly good (which also means Yumi > 2005 era Axiom M22ti). The 330's have a perceptible upper bass suck out that's audible in back-to-back auditions.
The 900 pound gorilla is the Dirac HD Player active equalization app running on my older iPad and iPod, going through my Apple EarPods. That program, as buggy as it is, equalizes the headphones to provide flat frequency response, sort of what SonarWorks is marketing today. The sound from the Dirac app is noticeably better than either Yumi (which sounds slightly harsh in the treble) and the 330's (with that huge upper bass suck out). Nevertheless, both loudspeakers nail the midrange vocals.
But all three of them sound great. I still stand by my decision to return the M22ti's, but I'm firmly looking forward to the active equalization active loudspeaker era of the future.
