Anyone with W4S amps and preamp

I would like to hear from anyone who uses or has heard the W4S amps and preamp together preferably with balanced connects in respect to other gear they may have owned. I am also interested in input from anyone who has used switching amps with other peamps with good results. I am using a Bel Canto S300ui while my tube amp is in for repair and it sounds surprisingly good. I am considering moving up the chain to mono's for greater resolution and dynamics. Thanks for the replies so far.

Thanks so much guys. This is exactly what I was hoping for. It has been a very long time since tubes have not been in the signal path of my stereo and I am twitchy. Unfortunately no way to audition similar setups within a 500 mile radius that I am aware of.