I don't like the 805s with Krell or NAD. I think The 805s are too dry to be paired with amps that white and analytical sounding. The NAD in particular is no good. It sounds a little bleached out and harsh to me. I think Classe is a natural choice for B&W. Tubes, although, would probably be better. It depends on what sort of sound your going for. This is just my opinion as I perhaps like a smoother sound than some.
