Full disclosure, Vandersteen Treo CT and 7 Mk2 owner, so i can certainly be ( rightly so ) accused of bias. Above comments are spot on. The Treo CT is a fatigue free speaker and easy to place in room, flat to 40 hz and a very easy load. I currently run my Treo with an ancient but highly modified MC240 tube amp. Your current pre/amp will work great. You might want to surf the Vandersteen owners forum to see the wide diversity of systems w Treo.
Finally, you have narrowed to three excellent choices all of which deliver value from trusted high end companies. Enjoy the music !
Jim