Joe, it would have been helpful to identify the sub, but just from the 40hz limit you report it would seem that this might not be a suitable addition to the M60s. I checked back and see that you're using Cambridge Audio two-channel amps. Since they have no built-in crossover for a sub, you would have to use the internal crossover in the sub. Since the LFE input bypasses the sub crossover, you'd have to use the "Normal" input. Since the sub is close to the M60 the 0 phase setting is probably better, but check the 180 to see if it gives stronger bass. Since running the M60s full-range means that the sub will be used just to reinforce the lowest bass(maybe not much with this sub),the cross-over should be set at or just above the 50hz mark(which may or may not be accurate).
