If you want more information on what John Stronczer has done with the new amps, watch the following video. He starts off by explaining how the S500 is designed, then goes on to explain the REF500 and REF1000MkII monoblocks:
http://uk.cinenow.com/videos/1861-bel-canto-s-500-stereo-power-amplifier-top-audio-milan-2008
http://uk.cinenow.com/videos/1861-bel-canto-s-500-stereo-power-amplifier-top-audio-milan-2008