What do you consider the most musical speakers—$15000 & under

To answer the OP Charney Audio does a great job with his tractrix designed rear loaded horns. They are both accurate and musical with very low distortion and wide range.  Don't take my word for it listen to them at The Capital Audiofest  next weekend.
http://charneyaudio.com/speakers.html
 

harbeth 7es3 very musical and still accurate imo!  

I haven't had the chance to listen to as many speakers as most of the posters here, but I'd personally be thrilled with either the ProAc D48R or Harbeth 40.2 and probably base my decision more on what the upstream equipment pairing & room placement options were over anything else.

Also Vandersteen.  

I'm pretty much in agreement with blindjim regarding the importance of amplifiers, etc. but would like to add that a more efficient speaker does allow a lot more flexibility in the budget required for great amplification.  (I have entry level ProAcs & a First Watt amp)

Those would be - Linkwitz Orions or LX521s or Legacy Aeris (if bought in the used market - below $15,000).