I owned a the ST150 and had it paired with the AI M3B. It smoked the McIntosh MC402 it replaced big time. Far better dynamics and PRAT for about half the price. VTL will also outperform the QS amps from what I recall (having owned the Silver 60's and Silver 90's). The only reason I sold it was to pick up a pair of vintage VTL compact 100's ( el34 based).
Good luck
Tony
Good luck
Tony