The stacked Quads have one of the best midrange offerings you can ever hope to find. Even still today, especially when driven with tubes. They have a sweet spot, which is quite narrow. So they need careful placement. They don't play particularly loud. So if you like chambermusic or small Jazz combos, they are the perfect speaker. Try to find Sequerra or Decca ribbons for the highs and a good sub and you have a system which in overall musicality and resolution is hard to beat.
The Divas play much louder, they are more dynamic, they are more extended in their frequency range, so if you like rock, pop, ore listen at louder levels, you are fine with them. They are less resolving, less coherent in the midband than the Quads. Hope this helps you along a bit. I personally would go for Quads any day....
