Adore the Academy, and have spent many, many glorious hours there over the years. But I also love the Kimmel auditorium. It really does deliver beautiful sound, and for a large place, is surprisingly intimate, probably because the acoustics are so immediate no matter where you are sitting. Both are treasures.
Have to say the sound at the Kimmel is great just about anywhere in the house, including in the first tier right over the stage above the cello section which is where we ended up with last-minute tickets for a Rachmaninoff concert a couple of years ago.....