If the Marantz has a pre-out you could use it as a line/phono preamplifier into the Mac power amp (connect the TT to phono and the DAC to a line input).
If it does nor have pre-out you might be able to add an inexpensive preamp (fed by the tape-out of the Marantz and then connected to the power amp).
Not ideal, but it would get you going (here's an inexpensive $50 preamp with two pairs of RCA inputs).
https://www.schiit.com/products/sys
DeKay