So as a dissenter I would buy (if you don't have a pair already) a pair of subwoofers that go deep (meaning not REL) and pair them with the Focal's. I would not choose the Magico S7's. The sound with this pairing is immense and with your McItosh equipment it would be even more luxurious,
For me I enjoy the musical quality of the Focal's, and I find most Magico speakers somewhat harsh sounding. (exacting, grating, forced...)
Good luck with you decision though, it's a great dilemma to have.