Why monoblocks?
Because they separately amplify the left and right signals without having to be in one box.
Because they allow you to use shorter speaker wires, which in turn, will result in less cable coloring.
Because using XLR cables (providing the circuitry follows AES standards) between amp and preamp minimizes signal loss. -I don't know if the Mac's are XLR, but going this route, I hope they are.
My 2.5 cents...
Bob