A industry insider (manufacturer of high-end limited production cables) once informed me that Janis subs really suck--too slow to keep up with Quads. FWIW, he uses two Entec subs with his system.
I don't know the Quad57s but I have a W3 system that I use with Merlin VSM-Ms and it sounds great. I also have a W1 system that I use with Tannoy System 8 studio monitors that are fairly efficient (92dB/w) and quite fast. Integration has never been a problem. Proper placement, volume, and phase settings are important.