I have just upgraded to a BAT Rex with my Krell 402. My previous preamp was the BAT VK-52se. The difference has been wonderful. More musical, even quieter background, more involving. The biggest difference is that I can listen much quieter than before. While everyone else is sleeping I can now listen with the same level of musical involvement as I did before only at a lower volume level. I am sleeping less, but listening more. A truly great, great preamp. I was told by the factory and my dealer that it would be a huge upgrade so one is always skeptical. After about fifteen minutes of listening the old preamp was being packed up. That was a month ago and it has been simply pure musical pleasure. I love the Krell amp. I do not want to go to monobloc amps for lots of reasons (the look of my listening room, my expensive and very long speaker cables-which run under the floor, the location of the equipment) so I was eager to find an upgrade that would make a difference. When you really look at high powered stereo amps there are not a lot of choices, and I think all are more similar than different. I was ready to BUY a VTL S-400 but no one would let me audition it at home for any kind of deal. Sorry guys, but this audiophile doesn't spend $20k on an amp without hearing it in the house, in the system. Krell bent over backward to make me happy, and now so has BAT. And it is not as hot running as I feared it might be.