Not sure about the floor standing speakers for rears. What about the Motion 2's for the surrounds and surround backs if you want to save some money. Otherwise, I would just go for the 4's for both surrounds and surround backs.
Let me ask, why ML's? Have you looked at other manufacturers?
Klipsch RF-52 II // RC-52 II // RS-42 II
Klipsch KG 2.5