I have a similar setup but with a Dave as the final part of the chain. The M scaler will add something more, no doubt. Will the uplift be worth it for the money though? Possibly! Try and get one to demo in your system.
One thing I can wholeheartedly recommend for next to no money though is the Fo.Q tape applied to the capacitors in the Zenith and Phoenix. No doubt about the difference, it really works. Bigger difference than power cables and thats saying something because as you have noticed, the Phoenix responds well to good powerJust cut squares to fit on top of the caps. I think lotususa do it too.