I've heard an awful lot of speakers in my time, on account of they get sent to my shop for audition and I hear them at shows as well.
For about 20 years now one of the best I've heard has been the Classic Audio Loudspeakers model T-3.3, which is what I've been playing for most of that time (started as T-3s). They have dual 15" woofers (which cut off at 20Hz) and field-coil magnet structures. The midrange in particular is quite nice- beryllium compression diaphragm with a Kapton surround; very fast and the first breakup is at 35KHz, so very smooth as well. The speakers are also easy to drive, being 16 ohms and 98 db 1 watt/1 meter.
There really isn't anything this speaker can't do. It can handle more power than I can throw at it, can play considerably louder than I ever need it to play and no part of the frequency spectrum is left to imagination. Its also very relaxed and detailed, even at high volume, but is equally comfortable imparting all the music at very low levels too. It is so undistorted that it is a bit disarming how loud its often playing- it certainly does not **sound** loud! Its only when you realized that you have to yell to be heard by someone right next to you that you realize how loud it might be playing.
Yet for all this the speaker is insanely musical. Its not particularly euphonic; instead I find it to be quite neutral, just like real music. It'll be quite a challenger to get them out of my living room- so far nothing is even on the horizon, which is not to say I've not heard other speakers that I could not live with for the rest of my life- I've heard a number of them. This one is simply the best of the crop.