From a sonic standpoint the best way is most likely connecting the tape outputs (left & right) of the MX-114 to the tuner inputs (left and right) of the MA-6200.
It would also be possible to connect the main outputs of the MX-114 to the tuner inputs of the MA-6200, but that would insert a lot of unnecessary circuitry into the signal path, including the volume control, balance control, and tone controls of the MX-114.
Regards,
-- Al