I'm using a W4S M-Pre (with a fixed volume setting) and dual M-Amps on my Xizi Fast 15s. Balanced Mogami interconnects, and Analysis Plus Oval Nines speaker cable. Same setup I used for the previous KEF LS50 setup, not your stereotypical high efficiency equipment. No noise coming out of the drivers and sounds great. I use a Mini DSP SHD Studio upstream as the preamp, which has a very fine volume adjustment. I had also tried a 2 watt tube amp, went back to the class D.
Heres another who used W4S with their OB:
https://www.enjoythemusic.com/RMAF_2016/Holt/Wyred_4_Sound_PureAudioProject_Spread_Spectrum_Technologies.htm
