I was a BAT dealer and had two VK-150se amps with both VK-40 and VK-51se preamps. While I absolutely loved the sound of this system the amps sounded lacking when compared to a Belles 350-A amp, and I mean lacking in bass slam, natural tones, fine detail, black background, etc. I then got a set of 350-A monoblocks at about 1500 watts each into 8 ohms and all of the qualities were multiplied. These sound like the best tube amp with way better tonal character and bass detail, and are truly fatigue free. Try a 350-A and you'll never go back to the tubes except for preamp purposes. Also the 21-A at $3000 smokes either of the best BAT preamps by being profoundly more open and dynamic, I used the BAT stuff to do A/B comparison demos.