They are an important ingredient of the KAB reference system. The Behringer Ultrafex 3100 is a great home theatre add-on. It features spectrum and spatial enhancement in one rack mount unit. Enhance bass, top octaves and close the seams between front and rear. The Aphex Tubessencetm equalizer is yet another way in which to enhance the sound of your audio system.
Tubes offer a soft sweetening to the upper octaves that many find just irresistable.